How get FeedItem with type TrackedChange

when i execute this:

Account acc = new Account(Name = 'newTest1',Phone = '+4444444444');insert acc;acc.Name = 'ChangedTestAnonimusAcc';acc.Phone = '+55555555555';update acc;List<FeedItem>  feedItems = [SELECT ID,Body,ParentId,Title,(SELECT ID, FieldName, OldValue, NewValue FROM FeedTrackedChanges ORDER BY ID DESC) FROM FeedItem WHERE Type='TrackedChange' AND ParentId =: acc.Id];System.debug(feedItems);

feedItems are empty(but I know FeedItem with type TrackedChange was created).I couldn't understand why.