Index: SoObjects/Appointments/SOGoAppointmentObject.m
--- SoObjects/Appointments/SOGoAppointmentObject.m.orig
+++ SoObjects/Appointments/SOGoAppointmentObject.m
@@ -1551,7 +1551,7 @@ inRecurrenceExceptionsForEvent: (iCalEvent *) theEvent
       if (addDelegate)
         {
           delegatedUID = [delegate uidInContext: context];
-          delegates = [NSArray arrayWithObject: delegate];
+          delegates = [NSMutableArray arrayWithObject: delegate];
           [event addToAttendees: delegate];
           
           if (delegatedUID)
