diff --git a/system/src/Grav/Common/Themes.php b/system/src/Grav/Common/Themes.php
index 4c5748be6..7c4c874ee 100644
--- a/system/src/Grav/Common/Themes.php
+++ b/system/src/Grav/Common/Themes.php
@@ -25,6 +25,8 @@ class Themes extends Iterator
 
     public function __construct(Grav $grav)
     {
+        parent::__construct();
+
         $this->grav = $grav;
         $this->config = $grav['config'];