diff --git a/library/Icinga/Data/Filter/Filter.php b/library/Icinga/Data/Filter/Filter.php
index 0688d2cc0..a5373a6bc 100644
--- a/library/Icinga/Data/Filter/Filter.php
+++ b/library/Icinga/Data/Filter/Filter.php
@@ -26,6 +26,8 @@ abstract class Filter
 
     abstract public function isChain();
 
+    abstract public function isEmpty();
+
     abstract function toQueryString();
 
     public function getUrlParams()