diff --git a/socket.io-client/socket.io-client.d.ts b/socket.io-client/socket.io-client.d.ts
index a3882bbd7a..205fb9e9ba 100644
--- a/socket.io-client/socket.io-client.d.ts
+++ b/socket.io-client/socket.io-client.d.ts
@@ -23,7 +23,7 @@ declare module SocketIOClient {
     interface Socket {
         on(event: string, fn: Function): Socket;
         once(event: string, fn: Function): Socket;
-        off(event: string, fn: Function): Socket;
+        off(event?: string, fn?: Function): Socket;
         emit(event: string, ...args: any[]): Socket;
         listeners(event: string): Function[];
         hasListeners(event: string): boolean;