diff --git a/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache b/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
index 058bdb5ca280..28520f752bef 100644
--- a/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
+++ b/modules/openapi-generator/src/main/resources/r/ApiResponse.mustache
@@ -50,6 +50,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/modules/openapi-generator/src/main/resources/r/api.mustache b/modules/openapi-generator/src/main/resources/r/api.mustache
index e81cd16951d3..6fef8bb79c55 100644
--- a/modules/openapi-generator/src/main/resources/r/api.mustache
+++ b/modules/openapi-generator/src/main/resources/r/api.mustache
@@ -515,7 +515,7 @@
       file_params["{{baseName}}"] <- httr::upload_file(`{{paramName}}`)
       {{/isHttr2}}
       {{#isHttr2}}
-      file_params["{{baseName}}"] <- curl::form_file(`{{paramName}}`)
+      file_params[["{{baseName}}"]] <- curl::form_file(`{{paramName}}`)
       {{/isHttr2}}
       {{/isFile}}
       {{/formParams}}
diff --git a/modules/openapi-generator/src/main/resources/r/api_client.mustache b/modules/openapi-generator/src/main/resources/r/api_client.mustache
index 3057ea2c4004..ace9861b42ee 100644
--- a/modules/openapi-generator/src/main/resources/r/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/r/api_client.mustache
@@ -335,7 +335,11 @@ ApiClient <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type
diff --git a/modules/openapi-generator/src/main/resources/r/libraries/httr2/api_client.mustache b/modules/openapi-generator/src/main/resources/r/libraries/httr2/api_client.mustache
index e888008f4597..1f003712d3c7 100644
--- a/modules/openapi-generator/src/main/resources/r/libraries/httr2/api_client.mustache
+++ b/modules/openapi-generator/src/main/resources/r/libraries/httr2/api_client.mustache
@@ -344,7 +344,11 @@ ApiClient  <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type.
diff --git a/samples/client/echo_api/r/R/api_client.R b/samples/client/echo_api/r/R/api_client.R
index 9fbeffaa59f6..78edb04b7d33 100644
--- a/samples/client/echo_api/r/R/api_client.R
+++ b/samples/client/echo_api/r/R/api_client.R
@@ -287,7 +287,11 @@ ApiClient <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type
diff --git a/samples/client/echo_api/r/R/api_response.R b/samples/client/echo_api/r/R/api_response.R
index 404f2ec8a9e8..999532bf3611 100644
--- a/samples/client/echo_api/r/R/api_response.R
+++ b/samples/client/echo_api/r/R/api_response.R
@@ -57,6 +57,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R-httr2-wrapper/R/api_client.R b/samples/client/petstore/R-httr2-wrapper/R/api_client.R
index 32aa262f5545..777f268794a3 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/api_client.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/api_client.R
@@ -333,7 +333,11 @@ ApiClient  <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type.
diff --git a/samples/client/petstore/R-httr2-wrapper/R/api_response.R b/samples/client/petstore/R-httr2-wrapper/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/api_response.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R-httr2-wrapper/R/pet_api.R b/samples/client/petstore/R-httr2-wrapper/R/pet_api.R
index 054a8c18952e..22bba7ad4116 100644
--- a/samples/client/petstore/R-httr2-wrapper/R/pet_api.R
+++ b/samples/client/petstore/R-httr2-wrapper/R/pet_api.R
@@ -1807,7 +1807,7 @@ PetApi <- R6::R6Class(
 
 
       form_params["additionalMetadata"] <- `additional_metadata`
-      file_params["file"] <- curl::form_file(`file`)
+      file_params[["file"]] <- curl::form_file(`file`)
       local_var_url_path <- "/pet/{petId}/uploadImage"
       if (!missing(`pet_id`)) {
         local_var_url_path <- gsub("\\{petId\\}", URLencode(as.character(`pet_id`), reserved = TRUE), local_var_url_path)
diff --git a/samples/client/petstore/R-httr2/R/api_client.R b/samples/client/petstore/R-httr2/R/api_client.R
index 32aa262f5545..777f268794a3 100644
--- a/samples/client/petstore/R-httr2/R/api_client.R
+++ b/samples/client/petstore/R-httr2/R/api_client.R
@@ -333,7 +333,11 @@ ApiClient  <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type.
diff --git a/samples/client/petstore/R-httr2/R/api_response.R b/samples/client/petstore/R-httr2/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R-httr2/R/api_response.R
+++ b/samples/client/petstore/R-httr2/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")
diff --git a/samples/client/petstore/R-httr2/R/pet_api.R b/samples/client/petstore/R-httr2/R/pet_api.R
index 9bc403759fdf..d79e53aa7189 100644
--- a/samples/client/petstore/R-httr2/R/pet_api.R
+++ b/samples/client/petstore/R-httr2/R/pet_api.R
@@ -1807,7 +1807,7 @@ PetApi <- R6::R6Class(
 
 
       form_params["additionalMetadata"] <- `additional_metadata`
-      file_params["file"] <- curl::form_file(`file`)
+      file_params[["file"]] <- curl::form_file(`file`)
       local_var_url_path <- "/pet/{petId}/uploadImage"
       if (!missing(`pet_id`)) {
         local_var_url_path <- gsub("\\{petId\\}", URLencode(as.character(`pet_id`), reserved = TRUE), local_var_url_path)
diff --git a/samples/client/petstore/R/R/api_client.R b/samples/client/petstore/R/R/api_client.R
index 2fa06773f021..3acfc70b63ef 100644
--- a/samples/client/petstore/R/R/api_client.R
+++ b/samples/client/petstore/R/R/api_client.R
@@ -316,7 +316,11 @@ ApiClient <- R6::R6Class(
     #' @return Deserialized object.
     #' @export
     deserialize = function(raw_response, return_type, pkg_env) {
-      resp_obj <- jsonlite::fromJSON(raw_response)
+      if (jsonlite::validate(raw_response)) {
+        resp_obj <- jsonlite::fromJSON(raw_response)
+      } else {
+        resp_obj <- raw_response
+      }
       self$deserializeObj(resp_obj, return_type, pkg_env)
     },
     #' Deserialize the response from jsonlite object based on the given type
diff --git a/samples/client/petstore/R/R/api_response.R b/samples/client/petstore/R/R/api_response.R
index b84d66f6ee0f..2916fd07d45a 100644
--- a/samples/client/petstore/R/R/api_response.R
+++ b/samples/client/petstore/R/R/api_response.R
@@ -56,6 +56,9 @@ ApiResponse <- R6::R6Class(
     #' @param to_encoding The target encoding of the return value.
     #' @export
     response_as_text = function(from_encoding = "", to_encoding = "UTF-8") {
+      if (is.null(self$response)) {
+        self$response <- charToRaw(jsonlite::toJSON("NULL"))
+      }
       text_response <- iconv(readBin(self$response, character()), from = from_encoding, to = to_encoding)
       if (is.na(text_response)) {
         warning("The response is binary and will not be converted to text.")