diff --git a/core/Core.php b/core/Core.php
index 7c5a489e7..c5566fbf0 100644
--- a/core/Core.php
+++ b/core/Core.php
@@ -275,6 +275,7 @@ gc_enable();
 require_once 'cache/Cache.php';
 require_once 'core/Object.php';
 require_once 'core/ClassInfo.php';
+require_once 'core/DAG.php';
 require_once 'core/Config.php';
 require_once 'view/TemplateGlobalProvider.php';
 require_once 'control/Director.php';