diff --git a/lib/server.js b/lib/server.js
index e34c3b9de..9de3de03e 100644
--- a/lib/server.js
+++ b/lib/server.js
@@ -311,7 +311,8 @@ Server.prototype._start = function (config, launcher, preprocess, fileList, webS
     // TODO(vojta): change the client to not send the event (if disconnected by purpose)
     var sockets = socketServer.sockets.sockets
 
-    sockets.forEach(function (socket) {
+    Object.keys(sockets).forEach(function (id) {
+      var socket = sockets[id]
       socket.removeAllListeners('disconnect')
       if (!socket.disconnected) {
         // Disconnect asynchronously. Socket.io mutates the `sockets.sockets` array