Accessing Unknown 'cornerRadius' Component of a Property

Wanted to create rounded corners for a component, done this before in another project. Suddenly it doesn't work any more:

button.layer.cornerRadius = 8.0f;

Forgot to include header:

#import <QuartzCore/QuartzCore.h>

Error code kind of hinted in that direction, I guess... Wasn't very obvious. Btw check that CoreGraphics.framework is already included in project.