diff --git a/main/inc/lib/usermanager.lib.php b/main/inc/lib/usermanager.lib.php
index fec45a050e..351f3adc80 100755
--- a/main/inc/lib/usermanager.lib.php
+++ b/main/inc/lib/usermanager.lib.php
@@ -298,7 +298,7 @@ class UserManager
         if (!empty($currentUserId)) {
             $creator_id = $currentUserId;
         } else {
-            $creator_id = '';
+            $creator_id = 0;
         }
 
         // First check wether the login already exists