diff --git a/plugins/admin/users/class_userManagement.inc b/plugins/admin/users/class_userManagement.inc
index dbe8270385a3d7f90d05c161e5d80507e5f6adcc..3deb397441ec2f8a13da3a76734e24a725766d75 100644
--- a/plugins/admin/users/class_userManagement.inc
+++ b/plugins/admin/users/class_userManagement.inc
@@ -103,7 +103,7 @@ class userManagement extends simpleManagement
       $this->filter->elements['SAMBA']['set']   = '';
     }
     if (empty($classes)) {
-      $this->filter->elements['FUNCTIONAL']['set']  = '';
+      $this->filter->elements['FUNCTIONAL']['set']  = '(objectClass=*)';
     } else {
       /* The FUNCTIONAL filter must not use inexisting classes */
       $this->filter->elements['FUNCTIONAL']['set']  = '(!(|(objectClass='.implode(')(objectClass=', $classes).')))';