diff --git a/socket.io/socket.io.d.ts b/socket.io/socket.io.d.ts
index 00d2f2688..bccff1c77 100644
--- a/socket.io/socket.io.d.ts
+++ b/socket.io/socket.io.d.ts
@@ -44,7 +44,7 @@ declare module SocketIO {
 
     interface Namespace extends NodeJS.EventEmitter {
         name: string;
-        connected: { [id: number]: Socket };
+        connected: { [id: string]: Socket };
         use(fn: Function): Namespace
 
         on(event: 'connection', listener: (socket: Socket) => void): any;