Index: SoObjects/Appointments/SOGoAppointmentFolder.m
--- SoObjects/Appointments/SOGoAppointmentFolder.m.orig
+++ SoObjects/Appointments/SOGoAppointmentFolder.m
@@ -466,9 +466,9 @@ static Class iCalEventK = nil;
         {
           sogoUser = [SOGoUser userWithLogin: theIdentifier roles: nil];
           if (sogoUser)
-            allUsers = [NSArray arrayWithObject: sogoUser];
+            allUsers = [NSMutableArray arrayWithObject: sogoUser];
           else
-            allUsers = [NSArray array];
+            allUsers = [NSMutableArray array];
         }
 
       for (i = 0; i < [allUsers count]; i++)
