Index: branches/RC/core/units/general/helpers/priority_helper.php
===================================================================
diff -u -N -r11576 -r11610
--- branches/RC/core/units/general/helpers/priority_helper.php	(.../priority_helper.php)	(revision 11576)
+++ branches/RC/core/units/general/helpers/priority_helper.php	(.../priority_helper.php)	(revision 11610)
@@ -29,6 +29,8 @@
 			}
 
 			$items_count = $this->Conn->GetOne($sql);
+
+			// instanceof is not used, because PHP4 doesn't support it
 			$current_priority = is_a($object, 'kDBList') ? 0 : $object->GetDBField('Priority');
 
 			if ($is_new || $current_priority == -($items_count+1)) {