diff --git a/lib/Doctrine/ORM/Mapping/Driver/AbstractFileDriver.php b/lib/Doctrine/ORM/Mapping/Driver/AbstractFileDriver.php
index b0197894b..d7adf5e9a 100644
--- a/lib/Doctrine/ORM/Mapping/Driver/AbstractFileDriver.php
+++ b/lib/Doctrine/ORM/Mapping/Driver/AbstractFileDriver.php
@@ -54,7 +54,7 @@ abstract class AbstractFileDriver implements Driver
      *
      * @var string
      */
-    protected $_fileExtension = '.php';
+    protected $_fileExtension;
     
     /** 
      * Initializes a new FileDriver that looks in the given path(s) for mapping