diff --git a/system/classes/config.class.php b/system/classes/config.class.php
index 56f063a82..c27a2f87d 100644
--- a/system/classes/config.class.php
+++ b/system/classes/config.class.php
@@ -33,6 +33,8 @@
 
 use Geeklog\ConfigInterface;
 
+require_once __DIR__ . '/ConfigInterface.php';
+
 class config implements ConfigInterface
 {
     /**