diff --git a/scripts/start.js b/scripts/start.js
index 0babf3478d03f4d6338766efedeb2b3ac3e7c01e..290e8bc9b5cef670e271119999c59b3796d5606d 100644
--- a/scripts/start.js
+++ b/scripts/start.js
@@ -19,7 +19,8 @@ var detect = require('detect-port');
 var prompt = require('./utils/prompt');
 var config = require('../config/webpack.config.dev');
 
-var DEFAULT_PORT = 3000;
+// Tools like Cloud9 rely on this
+var DEFAULT_PORT = process.env.PORT || 3000;
 var compiler;
 
 // TODO: hide this behind a flag and eliminate dead code on eject.