diff --git a/apps/calendar/lib/object.php b/apps/calendar/lib/object.php
index cc80a0bb708d3c0ef9b6f154dd467dc9b91bfe8a..9e4806227b06561c894ca0b7c8007c3a17e4a2b1 100644
--- a/apps/calendar/lib/object.php
+++ b/apps/calendar/lib/object.php
@@ -665,6 +665,9 @@ class OC_Calendar_Object{
 								$byday .= ',' . $weekofmonth . $days[$day];
 							}
 						}
+						if($byday == ''){
+							$byday = 'MO,TU,WE,TH,FR,SA,SU';
+						}
 						$rrule .= ';BYDAY=' . $byday;
 					}
 					break;