How to remove shadow in subviews when using shadow properties of CALayer

Question

I enabled shadow in my view as in the following:

UIView *contentView = ...;
contentView.layer.shadowOffset = CGSizeMake(0, 0);
contentView.layer.shadowRadius = 5;
contentView.layer.shadowOpacity = 0.8;

However, subviews that add to contentView are also displayed with a shadow which is not what I want. I only need the superview ("contentView") to have the shadow. What am I missing/need to do to get it display like that?