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 524623e31c8..74b5bd4f72e 100644
--- a/samples/client/petstore/typescript-fetch/builds/default/api.ts
+++ b/samples/client/petstore/typescript-fetch/builds/default/api.ts
@@ -36,7 +36,7 @@ export const COLLECTION_FORMATS = {
  * @interface FetchAPI
  */
 export interface FetchAPI {
-    (url: string, init?: any): Promise<any>;
+    (url: string, init?: any): Promise<Response>;
 }
 
 /**
@@ -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),
@@ -689,7 +691,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).addPet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -709,7 +711,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).deletePet(petId, apiKey, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -785,7 +787,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -806,7 +808,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePetWithForm(petId, name, status, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1188,7 +1191,7 @@ export const StoreApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = StoreApiFetchParamCreator(configuration).deleteOrder(orderId, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1637,7 +1644,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUser(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1656,7 +1663,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithArrayInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1675,7 +1682,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithListInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1694,7 +1701,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).deleteUser(username, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1751,7 +1758,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).logoutUser(options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1771,7 +1778,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).updateUser(username, body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
diff --git a/samples/client/petstore/typescript-fetch/builds/default/git_push.sh b/samples/client/petstore/typescript-fetch/builds/default/git_push.sh
index 1eb5727f6cd..a1ff4c9bcba 100644
--- a/samples/client/petstore/typescript-fetch/builds/default/git_push.sh
+++ b/samples/client/petstore/typescript-fetch/builds/default/git_push.sh
@@ -36,7 +36,7 @@ git_remote=`git remote`
 if [ "$git_remote" = "" ]; then # git remote not defined
 
     if [ "$GIT_TOKEN" = "" ]; then
-        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git crediential in your environment."
+        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git credential in your environment."
         git remote add origin https://github.com/${git_user_id}/${git_repo_id}.git
     else
         git remote add origin https://${git_user_id}:${GIT_TOKEN}@github.com/${git_user_id}/${git_repo_id}.git
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 524623e31c8..74b5bd4f72e 100644
--- a/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts
+++ b/samples/client/petstore/typescript-fetch/builds/es6-target/api.ts
@@ -36,7 +36,7 @@ export const COLLECTION_FORMATS = {
  * @interface FetchAPI
  */
 export interface FetchAPI {
-    (url: string, init?: any): Promise<any>;
+    (url: string, init?: any): Promise<Response>;
 }
 
 /**
@@ -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),
@@ -689,7 +691,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).addPet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -709,7 +711,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).deletePet(petId, apiKey, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -785,7 +787,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -806,7 +808,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePetWithForm(petId, name, status, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1188,7 +1191,7 @@ export const StoreApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = StoreApiFetchParamCreator(configuration).deleteOrder(orderId, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1637,7 +1644,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUser(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1656,7 +1663,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithArrayInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1675,7 +1682,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithListInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1694,7 +1701,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).deleteUser(username, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1751,7 +1758,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).logoutUser(options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1771,7 +1778,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).updateUser(username, body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
diff --git a/samples/client/petstore/typescript-fetch/builds/es6-target/git_push.sh b/samples/client/petstore/typescript-fetch/builds/es6-target/git_push.sh
index 1eb5727f6cd..a1ff4c9bcba 100644
--- a/samples/client/petstore/typescript-fetch/builds/es6-target/git_push.sh
+++ b/samples/client/petstore/typescript-fetch/builds/es6-target/git_push.sh
@@ -36,7 +36,7 @@ git_remote=`git remote`
 if [ "$git_remote" = "" ]; then # git remote not defined
 
     if [ "$GIT_TOKEN" = "" ]; then
-        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git crediential in your environment."
+        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git credential in your environment."
         git remote add origin https://github.com/${git_user_id}/${git_repo_id}.git
     else
         git remote add origin https://${git_user_id}:${GIT_TOKEN}@github.com/${git_user_id}/${git_repo_id}.git
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 524623e31c8..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
@@ -36,7 +36,7 @@ export const COLLECTION_FORMATS = {
  * @interface FetchAPI
  */
 export interface FetchAPI {
-    (url: string, init?: any): Promise<any>;
+    (url: string, init?: any): Promise<Response>;
 }
 
 /**
@@ -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),
@@ -689,7 +691,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        addPet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).addPet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -709,7 +711,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deletePet(petId: number, apiKey?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).deletePet(petId, apiKey, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -785,7 +787,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePet(body: Pet, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePet(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -806,7 +808,7 @@ export const PetApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updatePetWithForm(petId: number, name?: string, status?: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = PetApiFetchParamCreator(configuration).updatePetWithForm(petId, name, status, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1188,7 +1191,7 @@ export const StoreApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteOrder(orderId: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = StoreApiFetchParamCreator(configuration).deleteOrder(orderId, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -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),
@@ -1637,7 +1644,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUser(body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUser(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1656,7 +1663,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithArrayInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithArrayInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1675,7 +1682,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        createUsersWithListInput(body: Array<User>, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).createUsersWithListInput(body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1694,7 +1701,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        deleteUser(username: string, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).deleteUser(username, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1751,7 +1758,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        logoutUser(options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).logoutUser(options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
@@ -1771,7 +1778,7 @@ export const UserApiFp = function(configuration?: Configuration) {
          * @param {*} [options] Override http request option.
          * @throws {RequiredError}
          */
-        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<any> {
+        updateUser(username: string, body: User, options?: any): (fetch?: FetchAPI, basePath?: string) => Promise<Response> {
             const localVarFetchArgs = UserApiFetchParamCreator(configuration).updateUser(username, body, options);
             return (fetch: FetchAPI = portableFetch, basePath: string = BASE_PATH) => {
                 return fetch(basePath + localVarFetchArgs.url, localVarFetchArgs.options).then((response) => {
diff --git a/samples/client/petstore/typescript-fetch/builds/with-npm-version/git_push.sh b/samples/client/petstore/typescript-fetch/builds/with-npm-version/git_push.sh
index 1eb5727f6cd..a1ff4c9bcba 100644
--- a/samples/client/petstore/typescript-fetch/builds/with-npm-version/git_push.sh
+++ b/samples/client/petstore/typescript-fetch/builds/with-npm-version/git_push.sh
@@ -36,7 +36,7 @@ git_remote=`git remote`
 if [ "$git_remote" = "" ]; then # git remote not defined
 
     if [ "$GIT_TOKEN" = "" ]; then
-        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git crediential in your environment."
+        echo "[INFO] \$GIT_TOKEN (environment variable) is not set. Using the git credential in your environment."
         git remote add origin https://github.com/${git_user_id}/${git_repo_id}.git
     else
         git remote add origin https://${git_user_id}:${GIT_TOKEN}@github.com/${git_user_id}/${git_repo_id}.git