I'm trying to get my UITextView's corners to be masked by the rounded corners of the grouped UITableViewCell that contains it. Here's a screenshot of the cell as it currently stands

Here's some of the code I'm using to try to prevent the corners from overlapping my cells borders. I tried both

cell.contentView.layer.masksToBounds = YES;
cell.layer.masksToBounds = YES;  //tried this as a test, still doesn't work
detailTextView.clipsToBounds = YES;
[cell.contentView addSubview:detailTextView];

and

cell.layer.masksToBounds = YES;
cell.contentView.layer.masksToBounds = YES;
detailTextView.clipsToBounds = YES;
[cell addSubview:detailTextView];

This is obviously not working, what am I missing?