diff --git a/templates/base/http-clients/fetch-http-client.ejs b/templates/base/http-clients/fetch-http-client.ejs
index a1db3833..7660b593 100644
--- a/templates/base/http-clients/fetch-http-client.ejs
+++ b/templates/base/http-clients/fetch-http-client.ejs
@@ -104,8 +104,12 @@ export class HttpClient<SecurityDataType = unknown> {
     private contentFormatters: Record<ContentType, (input: any) => any> = {
         [ContentType.Json]: (input:any) => input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
         [ContentType.Text]: (input:any) => input !== null && typeof input !== "string" ? JSON.stringify(input) : input,
-        [ContentType.FormData]: (input: any) =>
-            Object.keys(input || {}).reduce((formData, key) => {
+        [ContentType.FormData]: (input: any) => {
+            if (input instanceof FormData) {
+                return input;
+            }
+
+            return Object.keys(input || {}).reduce((formData, key) => {
                 const property = input[key];
                 formData.append(
                     key,
@@ -116,7 +120,8 @@ export class HttpClient<SecurityDataType = unknown> {
                     `${property}`
                 );
                 return formData;
-            }, new FormData()),
+            }, new FormData());
+        },
         [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
     }
 
diff --git a/tests/__snapshots__/extended.test.ts.snap b/tests/__snapshots__/extended.test.ts.snap
index 8265c7c5..d8df57ec 100644
--- a/tests/__snapshots__/extended.test.ts.snap
+++ b/tests/__snapshots__/extended.test.ts.snap
@@ -2362,8 +2362,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -2374,7 +2378,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4398,8 +4403,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4410,7 +4419,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4632,8 +4642,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4644,7 +4658,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4901,8 +4916,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4913,7 +4932,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -5798,8 +5818,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -5810,7 +5834,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6534,8 +6559,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6546,7 +6575,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6846,8 +6876,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6858,7 +6892,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -7113,8 +7148,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -7125,7 +7164,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -7431,8 +7471,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -7443,7 +7487,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -8193,8 +8238,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -8205,7 +8254,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -8728,8 +8778,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -8740,7 +8794,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -8997,8 +9052,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -9009,7 +9068,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -9308,8 +9368,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -9320,7 +9384,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -9614,8 +9679,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -9626,7 +9695,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -9936,8 +10006,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -9948,7 +10022,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -10231,8 +10306,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -10243,7 +10322,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -45612,8 +45692,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -45624,7 +45708,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -59431,8 +59516,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -59443,7 +59532,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -60411,8 +60501,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -60423,7 +60517,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -60986,8 +61081,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -60998,7 +61097,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -61319,8 +61419,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -61331,7 +61435,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -61585,8 +61690,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -61597,7 +61706,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -61896,8 +62006,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -61908,7 +62022,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -62539,8 +62654,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -62551,7 +62670,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -63057,8 +63177,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -63069,7 +63193,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -63430,8 +63555,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -63442,7 +63571,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -63828,8 +63958,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -63840,7 +63974,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -64280,8 +64415,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -64292,7 +64431,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -64615,8 +64755,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -64627,7 +64771,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -64991,8 +65136,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -65003,7 +65152,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -65802,8 +65952,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -65814,7 +65968,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -66508,8 +66663,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -66520,7 +66679,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -66849,8 +67009,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -66861,7 +67025,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -67111,8 +67276,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -67123,7 +67292,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -67359,8 +67529,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -67371,7 +67545,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -67644,8 +67819,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -67656,7 +67835,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -68315,8 +68495,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -68327,7 +68511,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -69148,8 +69333,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -69160,7 +69349,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -70862,8 +71052,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -70874,7 +71068,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -71534,8 +71729,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -71546,7 +71745,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -71830,8 +72030,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -71842,7 +72046,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -72214,8 +72419,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -72226,7 +72435,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/__snapshots__/simple.test.ts.snap b/tests/__snapshots__/simple.test.ts.snap
index 3069a13c..b284f9a9 100644
--- a/tests/__snapshots__/simple.test.ts.snap
+++ b/tests/__snapshots__/simple.test.ts.snap
@@ -267,8 +267,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -279,7 +283,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -2431,8 +2436,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -2443,7 +2452,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -2665,8 +2675,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -2677,7 +2691,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -2908,8 +2923,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -2920,7 +2939,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -3288,8 +3308,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -3300,7 +3324,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4011,8 +4036,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4023,7 +4052,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4305,8 +4335,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4317,7 +4351,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4552,8 +4587,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4564,7 +4603,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -4814,8 +4854,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -4826,7 +4870,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -5150,8 +5195,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -5162,7 +5211,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -5757,8 +5807,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -5769,7 +5823,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6024,8 +6079,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6036,7 +6095,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6335,8 +6395,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6347,7 +6411,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6602,8 +6667,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6614,7 +6683,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -6883,8 +6953,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -6895,7 +6969,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -7162,8 +7237,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -7174,7 +7253,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -16046,8 +16126,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -16058,7 +16142,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -35983,8 +36068,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -35995,7 +36084,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -36511,8 +36601,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -36523,7 +36617,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -37150,8 +37245,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -37162,7 +37261,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -37487,8 +37587,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -37499,7 +37603,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -37727,8 +37832,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -37739,7 +37848,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -37974,8 +38084,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -37986,7 +38100,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -38422,8 +38537,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -38434,7 +38553,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -38864,8 +38984,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -38876,7 +39000,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -39170,8 +39295,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -39182,7 +39311,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -39477,8 +39607,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -39489,7 +39623,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -39820,8 +39955,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -39832,7 +39971,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -40149,8 +40289,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -40161,7 +40305,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -40425,8 +40570,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -40437,7 +40586,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -40793,8 +40943,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -40805,7 +40959,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -41437,8 +41592,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -41449,7 +41608,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -41745,8 +41905,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -41757,7 +41921,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -42017,8 +42182,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -42029,7 +42198,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -42246,8 +42416,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -42258,7 +42432,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -42499,8 +42674,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -42511,7 +42690,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -42876,8 +43056,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -42888,7 +43072,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -43475,8 +43660,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -43487,7 +43676,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -44614,8 +44804,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -44626,7 +44820,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -45351,8 +45546,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -45363,7 +45562,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -45664,8 +45864,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -45676,7 +45880,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
@@ -45918,8 +46123,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -45930,7 +46139,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/another-query-params/__snapshots__/basic.test.ts.snap b/tests/spec/another-query-params/__snapshots__/basic.test.ts.snap
index a7e14867..5b33a4d3 100644
--- a/tests/spec/another-query-params/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/another-query-params/__snapshots__/basic.test.ts.snap
@@ -138,8 +138,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -150,7 +154,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/custom-extensions/__snapshots__/basic.test.ts.snap b/tests/spec/custom-extensions/__snapshots__/basic.test.ts.snap
index 2debf655..4eb57c2b 100644
--- a/tests/spec/custom-extensions/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/custom-extensions/__snapshots__/basic.test.ts.snap
@@ -110,8 +110,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -122,7 +126,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/defaultAsSuccess/__snapshots__/basic.test.ts.snap b/tests/spec/defaultAsSuccess/__snapshots__/basic.test.ts.snap
index a246f891..e1539d54 100644
--- a/tests/spec/defaultAsSuccess/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/defaultAsSuccess/__snapshots__/basic.test.ts.snap
@@ -150,8 +150,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -162,7 +166,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/defaultResponse/__snapshots__/basic.test.ts.snap b/tests/spec/defaultResponse/__snapshots__/basic.test.ts.snap
index 3286c88a..4371c23c 100644
--- a/tests/spec/defaultResponse/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/defaultResponse/__snapshots__/basic.test.ts.snap
@@ -110,8 +110,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -122,7 +126,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/deprecated/__snapshots__/basic.test.ts.snap b/tests/spec/deprecated/__snapshots__/basic.test.ts.snap
index d8ca8953..cb2f877e 100644
--- a/tests/spec/deprecated/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/deprecated/__snapshots__/basic.test.ts.snap
@@ -110,8 +110,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -122,7 +126,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/dot-path-params/__snapshots__/basic.test.ts.snap b/tests/spec/dot-path-params/__snapshots__/basic.test.ts.snap
index e4aad5ec..91b4d0a3 100644
--- a/tests/spec/dot-path-params/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/dot-path-params/__snapshots__/basic.test.ts.snap
@@ -112,8 +112,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -124,7 +128,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/enumNamesAsValues/__snapshots__/basic.test.ts.snap b/tests/spec/enumNamesAsValues/__snapshots__/basic.test.ts.snap
index 4a857127..f56a3377 100644
--- a/tests/spec/enumNamesAsValues/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/enumNamesAsValues/__snapshots__/basic.test.ts.snap
@@ -302,8 +302,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -314,7 +318,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/extractRequestBody/__snapshots__/basic.test.ts.snap b/tests/spec/extractRequestBody/__snapshots__/basic.test.ts.snap
index 88abe76a..e563b6d3 100644
--- a/tests/spec/extractRequestBody/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/extractRequestBody/__snapshots__/basic.test.ts.snap
@@ -263,8 +263,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -275,7 +279,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/extractRequestParams/__snapshots__/basic.test.ts.snap b/tests/spec/extractRequestParams/__snapshots__/basic.test.ts.snap
index ffbbe4ed..a8f046a5 100644
--- a/tests/spec/extractRequestParams/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/extractRequestParams/__snapshots__/basic.test.ts.snap
@@ -185,8 +185,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -197,7 +201,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/extractResponseBody/__snapshots__/basic.test.ts.snap b/tests/spec/extractResponseBody/__snapshots__/basic.test.ts.snap
index 08404b86..6dc4c18c 100644
--- a/tests/spec/extractResponseBody/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/extractResponseBody/__snapshots__/basic.test.ts.snap
@@ -265,8 +265,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -277,7 +281,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/extractResponseError/__snapshots__/basic.test.ts.snap b/tests/spec/extractResponseError/__snapshots__/basic.test.ts.snap
index 20d0b77e..99da92c3 100644
--- a/tests/spec/extractResponseError/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/extractResponseError/__snapshots__/basic.test.ts.snap
@@ -260,8 +260,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -272,7 +276,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/jsAxios/__snapshots__/basic.test.ts.snap b/tests/spec/jsAxios/__snapshots__/basic.test.ts.snap
index d257b150..19d3a0a6 100644
--- a/tests/spec/jsAxios/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/jsAxios/__snapshots__/basic.test.ts.snap
@@ -63,8 +63,11 @@ export class HttpClient {
     [ContentType.Json]: (input) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -75,7 +78,8 @@ export class HttpClient {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input) => this.toQueryString(input),
   };
   mergeRequestParams(params1, params2) {
diff --git a/tests/spec/moduleNameFirstTag/__snapshots__/basic.test.ts.snap b/tests/spec/moduleNameFirstTag/__snapshots__/basic.test.ts.snap
index 4541e3c8..f64be153 100644
--- a/tests/spec/moduleNameFirstTag/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/moduleNameFirstTag/__snapshots__/basic.test.ts.snap
@@ -235,8 +235,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -247,7 +251,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/moduleNameIndex/__snapshots__/basic.test.ts.snap b/tests/spec/moduleNameIndex/__snapshots__/basic.test.ts.snap
index dadd562c..75f533c3 100644
--- a/tests/spec/moduleNameIndex/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/moduleNameIndex/__snapshots__/basic.test.ts.snap
@@ -235,8 +235,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -247,7 +251,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/on-insert-path-param/__snapshots__/basic.test.ts.snap b/tests/spec/on-insert-path-param/__snapshots__/basic.test.ts.snap
index 81245bc5..cb7951e5 100644
--- a/tests/spec/on-insert-path-param/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/on-insert-path-param/__snapshots__/basic.test.ts.snap
@@ -110,8 +110,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -122,7 +126,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/patch/__snapshots__/basic.test.ts.snap b/tests/spec/patch/__snapshots__/basic.test.ts.snap
index 95c6dc6c..d431bd8d 100644
--- a/tests/spec/patch/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/patch/__snapshots__/basic.test.ts.snap
@@ -1867,8 +1867,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -1879,7 +1883,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/responses/__snapshots__/basic.test.ts.snap b/tests/spec/responses/__snapshots__/basic.test.ts.snap
index 7a0746de..a0bec5bc 100644
--- a/tests/spec/responses/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/responses/__snapshots__/basic.test.ts.snap
@@ -150,8 +150,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -162,7 +166,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/singleHttpClient/__snapshots__/basic.test.ts.snap b/tests/spec/singleHttpClient/__snapshots__/basic.test.ts.snap
index d8ae13d8..e6a6707d 100644
--- a/tests/spec/singleHttpClient/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/singleHttpClient/__snapshots__/basic.test.ts.snap
@@ -110,8 +110,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -122,7 +126,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/sortTypes-false/__snapshots__/basic.test.ts.snap b/tests/spec/sortTypes-false/__snapshots__/basic.test.ts.snap
index 00daa650..1030d7a0 100644
--- a/tests/spec/sortTypes-false/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/sortTypes-false/__snapshots__/basic.test.ts.snap
@@ -1867,8 +1867,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -1879,7 +1883,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/sortTypes/__snapshots__/basic.test.ts.snap b/tests/spec/sortTypes/__snapshots__/basic.test.ts.snap
index ab7e8ad1..1fc72d45 100644
--- a/tests/spec/sortTypes/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/sortTypes/__snapshots__/basic.test.ts.snap
@@ -1867,8 +1867,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -1879,7 +1883,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/typeSuffixPrefix/__snapshots__/basic.test.ts.snap b/tests/spec/typeSuffixPrefix/__snapshots__/basic.test.ts.snap
index 2a0c78ef..5726cf74 100644
--- a/tests/spec/typeSuffixPrefix/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/typeSuffixPrefix/__snapshots__/basic.test.ts.snap
@@ -1867,8 +1867,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -1879,7 +1883,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };
 
diff --git a/tests/spec/unionEnums/__snapshots__/basic.test.ts.snap b/tests/spec/unionEnums/__snapshots__/basic.test.ts.snap
index 3a5d468e..6c479a96 100644
--- a/tests/spec/unionEnums/__snapshots__/basic.test.ts.snap
+++ b/tests/spec/unionEnums/__snapshots__/basic.test.ts.snap
@@ -122,8 +122,12 @@ export class HttpClient<SecurityDataType = unknown> {
     [ContentType.Json]: (input: any) =>
       input !== null && (typeof input === "object" || typeof input === "string") ? JSON.stringify(input) : input,
     [ContentType.Text]: (input: any) => (input !== null && typeof input !== "string" ? JSON.stringify(input) : input),
-    [ContentType.FormData]: (input: any) =>
-      Object.keys(input || {}).reduce((formData, key) => {
+    [ContentType.FormData]: (input: any) => {
+      if (input instanceof FormData) {
+        return input;
+      }
+
+      return Object.keys(input || {}).reduce((formData, key) => {
         const property = input[key];
         formData.append(
           key,
@@ -134,7 +138,8 @@ export class HttpClient<SecurityDataType = unknown> {
               : \`\${property}\`,
         );
         return formData;
-      }, new FormData()),
+      }, new FormData());
+    },
     [ContentType.UrlEncoded]: (input: any) => this.toQueryString(input),
   };