diff --git a/lib/Twig/Assets.php b/lib/Twig/Assets.php
index 1fdd68e3e0..cc32900788 100644
--- a/lib/Twig/Assets.php
+++ b/lib/Twig/Assets.php
@@ -1,7 +1,10 @@
 <?php
 namespace MailPoet\Twig;
 
-class Assets extends \Twig_Extension {
+class Assets
+  extends \Twig_Extension
+  implements \Twig_Extension_GlobalsInterface
+{
 
   private $_globals;