diff --git a/lib/http-proxy/index.js b/lib/http-proxy/index.js
index 0555e56..94b1849 100644
--- a/lib/http-proxy/index.js
+++ b/lib/http-proxy/index.js
@@ -135,18 +135,18 @@ ProxyServer.prototype.listen = function(port, hostname) {
 };
 
 ProxyServer.prototype.close = function(callback) {
+  var self = this;
   if (this._server) {
-    // Wrap callback to nullify server after all open connections are closed.
-    var callback_wrapper = function() {
-        this._server = null;
-
-        if (callback) {
-            callback(arguments);
-        }
-    };
-
-    this._server.close(callback_wrapper);
+    this._server.close(done);
   }
+
+  // Wrap callback to nullify server after all open connections are closed.
+  function done() {
+    self._server = null;
+    if (callback) {
+      callback.apply(null, arguments);
+    }
+  };
 };
 
 ProxyServer.prototype.before = function(type, passName, callback) {