diff --git a/src/creator.ts b/src/creator.ts
index a4faedd8..1e163727 100644
--- a/src/creator.ts
+++ b/src/creator.ts
@@ -538,7 +538,7 @@ export class BaseSlashCreator extends (EventEmitter as any as new () => TypedEve
     const signature = treq.headers['x-signature-ed25519'] as string;
     const timestamp = treq.headers['x-signature-timestamp'] as string;
 
-    const verified = await this._verify(JSON.stringify(treq.body), signature, timestamp);
+    const verified = await this._verify(treq.rawBody || JSON.stringify(treq.body), signature, timestamp);
 
     if (!verified) {
       this.emit('debug', 'A request failed to be verified');
diff --git a/src/server.ts b/src/server.ts
index 705427a9..2bb23254 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -61,6 +61,8 @@ export interface TransformedRequest {
   request: any;
   /** The response class from a Server, depending on what server it is. */
   response: any;
+  /** The raw string of the body. */
+  rawBody?: string;
 }
 
 /**
diff --git a/src/servers/bun.ts b/src/servers/bun.ts
index ea629ce1..bee249f7 100644
--- a/src/servers/bun.ts
+++ b/src/servers/bun.ts
@@ -34,7 +34,8 @@ export class BunServer extends Server {
           headers: Object.fromEntries(request.headers.entries()),
           body: body ? JSON.parse(body) : body,
           request,
-          response: null
+          response: null,
+          rawBody: body
         },
         async (response) => {
           if (response.files) {
diff --git a/src/servers/cfworker.ts b/src/servers/cfworker.ts
index a2191919..22407d12 100644
--- a/src/servers/cfworker.ts
+++ b/src/servers/cfworker.ts
@@ -29,7 +29,8 @@ export class CloudflareWorkerServer extends Server {
             headers: Object.fromEntries(request.headers.entries()),
             body: body ? JSON.parse(body) : body,
             request,
-            response: null
+            response: null,
+            rawBody: body
           },
           async (response) => {
             if (response.files) {
diff --git a/src/servers/fastify.ts b/src/servers/fastify.ts
index efadcf1b..37a41405 100644
--- a/src/servers/fastify.ts
+++ b/src/servers/fastify.ts
@@ -30,27 +30,41 @@ export class FastifyServer extends Server {
 
   /** @private */
   createEndpoint(path: string, handler: ServerRequestHandler) {
-    this.app.post(path, (req: any, res: any) =>
-      handler(
-        {
-          headers: req.headers,
-          body: req.body,
-          request: req,
-          response: res
-        },
-        async (response) => {
-          res.status(response.status || 200);
-          if (response.headers) res.headers(response.headers);
-          if (response.files) {
-            const data = new MultipartData();
-            res.header('Content-Type', 'multipart/form-data; boundary=' + data.boundary);
-            for (const i in response.files) data.attach(`files[${i}]`, response.files[i].file, response.files[i].name);
-            data.attach('payload_json', JSON.stringify(response.body));
-            res.send(Buffer.concat(data.finish()));
-          } else res.send(response.body);
+    this.app.register(async (app: any) => {
+      // Capture and set the raw payload with a scoped parser
+      app.addContentTypeParser(
+        'application/json',
+        { parseAs: 'string', asString: true },
+        (request: any, payload: any, done: any) => {
+          request.rawBody = payload;
+          app.getDefaultJsonParser('remove', 'remove')(request, payload, done);
         }
-      )
-    );
+      );
+
+      app.post(path, (req: any, res: any) =>
+        handler(
+          {
+            headers: req.headers,
+            body: req.body,
+            request: req,
+            response: res,
+            rawBody: req.rawBody
+          },
+          async (response) => {
+            res.status(response.status || 200);
+            if (response.headers) res.headers(response.headers);
+            if (response.files) {
+              const data = new MultipartData();
+              res.header('Content-Type', 'multipart/form-data; boundary=' + data.boundary);
+              for (const i in response.files)
+                data.attach(`files[${i}]`, response.files[i].file, response.files[i].name);
+              data.attach('payload_json', JSON.stringify(response.body));
+              res.send(Buffer.concat(data.finish()));
+            } else res.send(response.body);
+          }
+        )
+      );
+    });
   }
 
   /** @private */
diff --git a/src/servers/lambda.ts b/src/servers/lambda.ts
index 04211b0c..ac993560 100644
--- a/src/servers/lambda.ts
+++ b/src/servers/lambda.ts
@@ -33,7 +33,8 @@ export class AWSLambdaServer extends Server {
         headers: splitHeaders(event.headers),
         body: event.body ? JSON.parse(event.body) : {},
         request: event,
-        response: callback
+        response: callback,
+        rawBody: event.body ?? ''
       },
       async (response) => {
         const responseHeaders = joinHeaders(response.headers);