diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index 2ecf2b6dfd..de1cbbaa30 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -375,7 +375,7 @@ class calendar_uiforms extends calendar_ui
 								$id = $uid;
 								$type = 'u';
 							}
-							else
+							elseif ($uid)
 							{
 								$id = substr($uid,1);
 								$type = $uid[0];