diff --git a/src/Symfony/Component/HttpKernel/Kernel.php b/src/Symfony/Component/HttpKernel/Kernel.php
index 325ef4d443c6..b05e877d7ba5 100644
--- a/src/Symfony/Component/HttpKernel/Kernel.php
+++ b/src/Symfony/Component/HttpKernel/Kernel.php
@@ -868,7 +868,7 @@ protected function dumpContainer(ConfigCache $cache, ContainerBuilder $container
             $fs->dumpFile($dir.$file, $code);
             @chmod($dir.$file, 0666 & ~umask());
         }
-        $legacyFile = \dirname($dir.$file).'.legacy';
+        $legacyFile = \dirname($dir.key($content)).'.legacy';
         if (file_exists($legacyFile)) {
             @unlink($legacyFile);
         }