diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
index 43d5d081a8..ca1f829f10 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
@@ -1050,6 +1050,7 @@ class FrameworkExtension extends Extension
             $container->removeDefinition('session.storage.metadata_bag');
             $container->removeDefinition('session.storage.native');
             $container->removeDefinition('session.storage.php_bridge');
+            $container->removeDefinition('session.storage.mock_file');
             $container->removeAlias('session.storage.filesystem');
         }