diff --git a/Readme.md b/Readme.md
index 66cda4722c..631b7d88dc 100644
--- a/Readme.md
+++ b/Readme.md
@@ -113,7 +113,7 @@ io.listen(3000);
 Starting with **3.0**, express applications have become request handler
 functions that you pass to `http` or `http` `Server` instances. You need
 to pass the `Server` to `socket.io`, and not the express application
-function.
+function. Also make sure to call `.listen` on the `server`, not the `app`.
 
 ```js
 var app = require('express')();