diff --git a/apps/calendar/export.php b/apps/calendar/export.php
index 0756e1df20e3cda05b31ff760e28d8c124b1f329..5780d191a57bd308c2aa7ac0344c67801aaa28d3 100755
--- a/apps/calendar/export.php
+++ b/apps/calendar/export.php
@@ -14,6 +14,10 @@ $event = isset($_GET['eventid']) ? $_GET['eventid'] : NULL;
 $nl = "\r\n";
 if(isset($cal)){
 	$calendar = OC_Calendar_App::getCalendar($cal, true);
+	if(!$calendar){
+		header('HTTP/1.0 404 Not Found');
+		exit;
+	}
 	$calobjects = OC_Calendar_Object::all($cal);
 	header('Content-Type: text/Calendar');
 	header('Content-Disposition: inline; filename=' . $calendar['displayname'] . '.ics'); 
@@ -22,6 +26,10 @@ if(isset($cal)){
 	}
 }elseif(isset($event)){
 	$data = OC_Calendar_App::getEventObject($_GET['eventid'], true);
+	if(!$data){
+		header('HTTP/1.0 404 Not Found');
+		exit;
+	}
 	$calendarid = $data['calendarid'];
 	$calendar = OC_Calendar_App::getCalendar($calendarid);
 	header('Content-Type: text/Calendar');