diff --git a/src/main/resources/handlebars/typescript-fetch/api.mustache b/src/main/resources/handlebars/typescript-fetch/api.mustache
index 1c84f1edcb..f67dfaf549 100644
--- a/src/main/resources/handlebars/typescript-fetch/api.mustache
+++ b/src/main/resources/handlebars/typescript-fetch/api.mustache
@@ -44,7 +44,7 @@ export interface FetchArgs {
  * @class BaseAPI
  */
 export class BaseAPI {
-    protected configuration: Configuration;
+    protected configuration?: Configuration;
 
     constructor(configuration?: Configuration, protected basePath: string = BASE_PATH, protected fetch: FetchAPI = isomorphicFetch) {
         if (configuration) {