diff --git a/lib/Doctrine/ORM/Proxy/ProxyFactory.php b/lib/Doctrine/ORM/Proxy/ProxyFactory.php
index ed5d1560c..7e01ad7c2 100644
--- a/lib/Doctrine/ORM/Proxy/ProxyFactory.php
+++ b/lib/Doctrine/ORM/Proxy/ProxyFactory.php
@@ -143,7 +143,7 @@ class ProxyFactory
      * @param $proxyClassName
      * @param $file The path of the file to write to.
      */
-    private function _generateProxyClass($class, $fileName, $file)
+    private function _generateProxyClass(ClassMetadata $class, $fileName, $file)
     {
         $methods = $this->_generateMethods($class);
         $sleepImpl = $this->_generateSleep($class);