diff --git a/types/webpack-serve/index.d.ts b/types/webpack-serve/index.d.ts
index f0426c5ad7..cc83147ad2 100644
--- a/types/webpack-serve/index.d.ts
+++ b/types/webpack-serve/index.d.ts
@@ -2,6 +2,7 @@
 // Project: https://github.com/webpack-contrib/webpack-serve
 // Definitions by: Ryan Clark <https://github.com/rynclark>
 //                 Jokcy <https://github.com/Jokcy>
+//                 ZSkycat <https://github.com/ZSkycat>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 // TypeScript Version: 2.3
 
@@ -21,16 +22,14 @@ declare module 'webpack' {
   }
 }
 
-declare function WebpackServe(
-  options: WebpackServe.Options
-): Promise<WebpackServe.Instance>;
+declare function WebpackServe(options: WebpackServe.Options): Promise<WebpackServe.Instance>;
 
 declare namespace WebpackServe {
   interface WebpackServeOpen {
     /** Name of the browser to open */
-    app: string;
+    app?: string;
     /** Path on the server to open */
-    path: string;
+    path?: string;
   }
 
   interface WebpackServeMiddleware {