diff --git a/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php b/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
index 2d543ed2b4..5f7f1f38c1 100644
--- a/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
+++ b/src/Symfony/Component/Debug/FatalErrorHandler/ClassNotFoundFatalErrorHandler.php
@@ -125,7 +125,7 @@ class ClassNotFoundFatalErrorHandler implements FatalErrorHandlerInterface
             }
         }
 
-        return $classes;
+        return array_unique($classes);
     }
 
     /**