diff --git a/src/Symfony/Bundle/FrameworkBundle/CacheWarmer/ClassCacheCacheWarmer.php b/src/Symfony/Bundle/FrameworkBundle/CacheWarmer/ClassCacheCacheWarmer.php
index 6e0cd41745..54b9b3395e 100644
--- a/src/Symfony/Bundle/FrameworkBundle/CacheWarmer/ClassCacheCacheWarmer.php
+++ b/src/Symfony/Bundle/FrameworkBundle/CacheWarmer/ClassCacheCacheWarmer.php
@@ -34,6 +34,10 @@ class ClassCacheCacheWarmer implements CacheWarmerInterface
             return;
         }
 
+        if (file_exists($cacheDir.'/classes.php')) {
+            return;
+        }
+
         ClassCollectionLoader::load(include($classmap), $cacheDir, 'classes', false);
     }