diff --git a/ws/ws.d.ts b/ws/ws.d.ts
index 235b538030..6b94bee19d 100644
--- a/ws/ws.d.ts
+++ b/ws/ws.d.ts
@@ -88,16 +88,16 @@ declare module "ws" {
     }
 
     namespace WebSocket {
+                
+        type VerifyClientCallbackSync = (info: {origin: string; secure: boolean; req: http.ServerRequest}) => boolean;
+        type VerifyClientCallbackAsync = (info: {origin: string; secure: boolean; req: http.ServerRequest}
+                                            , callback: (res: boolean) => void) => void;
+
         export interface IServerOptions {
             host?: string;
             port?: number;
             server?: http.Server;
-            verifyClient?: (
-                ((info: {origin: string; secure: boolean; req: http.ServerRequest}) => boolean)
-                |
-                ((info: {origin: string; secure: boolean; req: http.ServerRequest},
-                    callback: (res: boolean) => void) => void)
-            );
+            verifyClient?: VerifyClientCallbackAsync | VerifyClientCallbackSync;
             handleProtocols?: any;
             path?: string;
             noServer?: boolean;