diff --git a/calendar/inc/class.calendar_boupdate.inc.php b/calendar/inc/class.calendar_boupdate.inc.php
index c463f27ddd..5e3cfe73e1 100644
--- a/calendar/inc/class.calendar_boupdate.inc.php
+++ b/calendar/inc/class.calendar_boupdate.inc.php
@@ -1885,6 +1885,11 @@ class calendar_boupdate extends calendar_bo
 		{
 			return false;
 		}
+		// make sure to not set a recur_date for a non-recurring event (as recur_date has to be 0, for non-recurring events!)
+		if ($recur_date && ($event = $event || $this->read($cal_id, null, $ignore_acl)) && empty($event['recur_type']))
+		{
+			$recur_date = 0;
+		}
 		$quantity = $role = null;
 		calendar_so::split_status($status, $quantity, $role);
 		if ($this->log)