diff --git a/modules/swagger-codegen/src/main/resources/typescript-angular/api.service.mustache b/modules/swagger-codegen/src/main/resources/typescript-angular/api.service.mustache
index b4a04c98cb2..9467bf25921 100644
--- a/modules/swagger-codegen/src/main/resources/typescript-angular/api.service.mustache
+++ b/modules/swagger-codegen/src/main/resources/typescript-angular/api.service.mustache
@@ -263,7 +263,7 @@ export class {{classname}} {
         const canConsumeForm = this.canConsumeForm(consumes);
 
 {{^useHttpClient}}
-        let formParams: { append(param: string, value: any): void; };
+        let formParams: { append(param: string, value: any): any; };
 {{/useHttpClient}}
 {{#useHttpClient}}
         let formParams: { append(param: string, value: any): void | HttpParams; };