diff --git a/include/class.list.php b/include/class.list.php
index b52c4f72186606b869a16d70309f36df14d98322..c512e796d705e6d204e26dcdc58e57c67a22aef6 100644
--- a/include/class.list.php
+++ b/include/class.list.php
@@ -1458,7 +1458,7 @@ implements CustomListItem, TemplateVariable {
         return  parent::create($ht);
     }
 
-    static function lookup($var, $list= false) {
+    static function lookup($var, $list=null) {
 
         if (!($item = parent::lookup($var)))
             return null;