diff --git a/modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache b/modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache
index 1745c5dcddf..476a1c767fd 100644
--- a/modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache
+++ b/modules/swagger-codegen/src/main/resources/typescript-fetch/api.mustache
@@ -212,7 +212,12 @@ export const {{classname}}FetchParamCreator = function (configuration?: Configur
 
     {{/hasFormParams}}
     {{#bodyParam}}
+            {{^consumes}}
             localVarHeaderParameter['Content-Type'] = 'application/json';
+            {{/consumes}}
+            {{#consumes.0}}
+            localVarHeaderParameter['Content-Type'] = '{{mediaType}}';
+            {{/consumes.0}}
 
     {{/bodyParam}}
             localVarUrlObj.query = Object.assign({}, localVarUrlObj.query, localVarQueryParameter, options.query);
@@ -223,7 +228,8 @@ export const {{classname}}FetchParamCreator = function (configuration?: Configur
             localVarRequestOptions.body = localVarFormParams.toString();
     {{/hasFormParams}}
     {{#bodyParam}}
-            localVarRequestOptions.body = JSON.stringify({{paramName}} || {});
+            const needsSerialization = (<any>"{{dataType}}" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify({{paramName}} || {}) : ({{paramName}} || "");
     {{/bodyParam}}
 
             return {
diff --git a/samples/client/petstore/typescript-fetch/builds/default/api.ts b/samples/client/petstore/typescript-fetch/builds/default/api.ts
index 6cc673e543c..74b5bd4f72e 100644
--- a/samples/client/petstore/typescript-fetch/builds/default/api.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default/api.ts
@@ -360,7 +360,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -562,7 +563,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1165,7 +1167,8 @@ export const StoreApiFetchParamCreator = function (configuration?: Configuration
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Order" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1393,7 +1396,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1424,7 +1428,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1455,7 +1460,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1614,7 +1620,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
diff --git a/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts b/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts
index 6cc673e543c..74b5bd4f72e 100644
--- a/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts
+++ b/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts
@@ -360,7 +360,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -562,7 +563,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1165,7 +1167,8 @@ export const StoreApiFetchParamCreator = function (configuration?: Configuration
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Order" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1393,7 +1396,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1424,7 +1428,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1455,7 +1460,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1614,7 +1620,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
diff --git a/samples/client/petstore/typescript-fetch/builds/with-npm-version/api.ts b/samples/client/petstore/typescript-fetch/builds/with-npm-version/api.ts
index 6cc673e543c..74b5bd4f72e 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-npm-version/api.ts
+++ b/samples/client/petstore/typescript-fetch/builds/with-npm-version/api.ts
@@ -360,7 +360,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -562,7 +563,8 @@ export const PetApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Pet" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1165,7 +1167,8 @@ export const StoreApiFetchParamCreator = function (configuration?: Configuration
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Order" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1393,7 +1396,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1424,7 +1428,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1455,7 +1460,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"Array&lt;User&gt;" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),
@@ -1614,7 +1620,8 @@ export const UserApiFetchParamCreator = function (configuration?: Configuration)
             // fix override query string Detail: https://stackoverflow.com/a/7517673/1077943
             delete localVarUrlObj.search;
             localVarRequestOptions.headers = Object.assign({}, localVarHeaderParameter, options.headers);
-            localVarRequestOptions.body = JSON.stringify(body || {});
+            const needsSerialization = (<any>"User" !== "string") || localVarRequestOptions.headers['Content-Type'] === 'application/json';
+            localVarRequestOptions.body =  needsSerialization ? JSON.stringify(body || {}) : (body || "");
 
             return {
                 url: url.format(localVarUrlObj),