diff --git a/calendar/js/et2_widget_event.js b/calendar/js/et2_widget_event.js
index 388832adbe..42fab5f947 100644
--- a/calendar/js/et2_widget_event.js
+++ b/calendar/js/et2_widget_event.js
@@ -755,7 +755,7 @@ var et2_calendar_event = /** @class */ (function (_super) {
                 if (matching_participant.length > 0) {
                     return this._status_check(event, filter, matching_participant);
                 }
-                else if (filter == 'owner' && resource && resource.resources.indexOf(event.owner)) {
+                else if (filter == 'owner' && resource && resource.resources && resource.resources.indexOf(event.owner)) {
                     // owner param was a group but event is owned by someone in that group
                     return true;
                 }
diff --git a/calendar/js/et2_widget_event.ts b/calendar/js/et2_widget_event.ts
index 3c45e634be..db0004823d 100644
--- a/calendar/js/et2_widget_event.ts
+++ b/calendar/js/et2_widget_event.ts
@@ -974,7 +974,7 @@ export class et2_calendar_event extends et2_valueWidget implements et2_IDetached
 				{
 					return this._status_check(event, filter, matching_participant);
 				}
-				else if (filter == 'owner' && resource && resource.resources.indexOf(event.owner))
+				else if (filter == 'owner' && resource && resource.resources && resource.resources.indexOf(event.owner))
 				{
 					// owner param was a group but event is owned by someone in that group
 					return true;