diff --git a/calendar/inc/class.bocalendar.inc.php b/calendar/inc/class.bocalendar.inc.php
index 09c5504fa7..43ec1e1bfb 100755
--- a/calendar/inc/class.bocalendar.inc.php
+++ b/calendar/inc/class.bocalendar.inc.php
@@ -764,7 +764,7 @@
 			@reset($event['participants']);
 			$uim = False;
 			$security_equals = $GLOBALS['phpgw']->accounts->membership($user);
-			while(!$uim && $security_equals && list($participant,$status) = each($event['participants']))
+			while(!$uim && $event['participants'] && $security_equals && list($participant,$status) = each($event['participants']))
 			{
 				if($GLOBALS['phpgw']->accounts->get_type($participant) == 'g')
 				{