diff --git a/calendar/inc/class.calendar_ical.inc.php b/calendar/inc/class.calendar_ical.inc.php
index 7e7e5a32a6..a63273f4fe 100644
--- a/calendar/inc/class.calendar_ical.inc.php
+++ b/calendar/inc/class.calendar_ical.inc.php
@@ -1800,6 +1800,7 @@ class calendar_ical extends calendar_boupdate
 					case 'G':
 					case 'P':
 					case 0:
+					case -1:
 						$owner = $this->user;
 						break;
 					default:
diff --git a/calendar/inc/class.calendar_sif.inc.php b/calendar/inc/class.calendar_sif.inc.php
index 46795063ed..333ef5bd66 100644
--- a/calendar/inc/class.calendar_sif.inc.php
+++ b/calendar/inc/class.calendar_sif.inc.php
@@ -1218,6 +1218,7 @@ class calendar_sif extends calendar_boupdate
 					case 'G':
 					case 'P':
 					case 0:
+					case -1:
 						$owner = $this->user;
 						break;
 					default: