diff --git a/lib/middleware/session.js b/lib/middleware/session.js
index fb8b17886..66c0bce7b 100644
--- a/lib/middleware/session.js
+++ b/lib/middleware/session.js
@@ -248,7 +248,12 @@ function session(options){
     // set-cookie
     var writeHead = res.writeHead;
     res.writeHead = function(){
-      if (!req.session) return;
+      if (!req.session) {
+        debug('no session');
+        writeHead.apply(res, arguments);
+        return;
+      }
+
       var cookie = req.session.cookie
         , proto = (req.headers['x-forwarded-proto'] || '').split(',')[0].toLowerCase().trim()
         , tls = req.connection.encrypted || (trustProxy && 'https' == proto)