diff --git a/types/ws/index.d.ts b/types/ws/index.d.ts
index b99f9e4d88..eea68c0b16 100644
--- a/types/ws/index.d.ts
+++ b/types/ws/index.d.ts
@@ -44,8 +44,8 @@ declare class WebSocket extends events.EventEmitter {
     close(code?: number, data?: string): void;
     ping(data?: any, mask?: boolean, cb?: (err: Error) => void): void;
     pong(data?: any, mask?: boolean, cb?: (err: Error) => void): void;
-    send(data: any, cb?: (err: Error) => void): void;
-    send(data: any, options: { mask?: boolean; binary?: boolean; compress?: boolean; fin?: boolean }, cb?: (err: Error) => void): void;
+    send(data: any, cb?: (err?: Error) => void): void;
+    send(data: any, options: { mask?: boolean; binary?: boolean; compress?: boolean; fin?: boolean }, cb?: (err?: Error) => void): void;
     terminate(): void;
 
     // HTML5 WebSocket events
diff --git a/types/ws/ws-tests.ts b/types/ws/ws-tests.ts
index bc62d9de98..7819236855 100644
--- a/types/ws/ws-tests.ts
+++ b/types/ws/ws-tests.ts
@@ -22,6 +22,8 @@ import * as https from 'https';
     wss.on('connection', (ws, req) => {
         ws.on('message', (message) => console.log('received: %s', message));
         ws.send('something');
+        ws.send('something', (error?: Error) => {});
+        ws.send('something', {}, (error?: Error) => {});
     });
 
     wss.on('upgrade', (res) => {