diff --git a/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache b/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
index 25a2731a3d3e..9902d44bb382 100644
--- a/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
+++ b/modules/openapi-generator/src/main/resources/typescript-fetch/runtime.mustache
@@ -211,10 +211,12 @@ export interface RequestOpts {
     body?: HTTPBody;
 }
 
+{{^withoutRuntimeChecks}}
 export function exists(json: any, key: string) {
     const value = json[key];
     return value !== null && value !== undefined;
 }
+{{/withoutRuntimeChecks}}
 
 export function querystring(params: HTTPQuery, prefix: string = ''): string {
     return Object.keys(params)
@@ -238,12 +240,14 @@ export function querystring(params: HTTPQuery, prefix: string = ''): string {
         .join('&');
 }
 
+{{^withoutRuntimeChecks}}
 export function mapValues(data: any, fn: (item: any) => any) {
   return Object.keys(data).reduce(
     (acc, key) => ({ ...acc, [key]: fn(data[key]) }),
     {}
   );
 }
+{{/withoutRuntimeChecks}}
 
 export function canConsumeForm(consumes: Consume[]): boolean {
     for (const consume of consumes) {
diff --git a/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts b/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
index 50d885957985..5b3f9d13f6c4 100644
--- a/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
+++ b/samples/client/petstore/typescript-fetch/builds/without-runtime-checks/src/runtime.ts
@@ -222,10 +222,6 @@ export interface RequestOpts {
     body?: HTTPBody;
 }
 
-export function exists(json: any, key: string) {
-    const value = json[key];
-    return value !== null && value !== undefined;
-}
 
 export function querystring(params: HTTPQuery, prefix: string = ''): string {
     return Object.keys(params)
@@ -249,12 +245,6 @@ export function querystring(params: HTTPQuery, prefix: string = ''): string {
         .join('&');
 }
 
-export function mapValues(data: any, fn: (item: any) => any) {
-  return Object.keys(data).reduce(
-    (acc, key) => ({ ...acc, [key]: fn(data[key]) }),
-    {}
-  );
-}
 
 export function canConsumeForm(consumes: Consume[]): boolean {
     for (const consume of consumes) {