ios - Corner radius in UIImageView inside UICollectionViewCell -

i'm setting corner radius of uiimageview inside uicollectionviewcell using user-defined attributes in interface builder. of time corner radius renders correctly, corners colored in seemingly random color:

i've tried overriding layoutsubviews in subclass of uicollectionviewcell , setting corner radius there (as described in other stack overflow questions). i've tried setting corner radius in couple other places, nothing seems work. how can fix this?

wrapping uiimageview uiview , setting corner radius of uiview ended resolving issue. still curious why problem occurring though...