diff --git a/lib/Server.js b/lib/Server.js
index 0030fa560d..536373bdde 100644
--- a/lib/Server.js
+++ b/lib/Server.js
@@ -883,9 +883,9 @@ Server.prototype._watch = function (watchPath) {
   this.contentBaseWatchers.push(watcher);
 };
 
-Server.prototype.invalidate = function () {
+Server.prototype.invalidate = function (callback) {
   if (this.middleware) {
-    this.middleware.invalidate();
+    this.middleware.invalidate(callback);
   }
 };