diff --git a/lib/index.js b/lib/index.js
index 9f73d5faf8..c86f4e92c6 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -321,6 +321,7 @@ Server.prototype.serve = function(req, res){
   }
 
   debug('serve client source');
+  res.setHeader("Cache-Control", "public, max-age=0");
   res.setHeader('Content-Type', 'application/javascript');
   res.setHeader('ETag', expectedEtag);
   res.setHeader('X-SourceMap', 'socket.io.js.map');