Vector image in UIButton

Hello,

I am trying to simply add a vector pdf icon to UIButton. What I get is that in iOS Simulator (9.2) the images are visible only on click but not in default state. My code in viewDidLoad() for the button is:

button.setImage(UIImage(named: "icons-final_aktuality"), forState: UIControlState.Normal)

button.imageView?.contentMode = UIViewContentMode.ScaleAspectFit

I have also tried to solve this via Interface builder but the result is same. The images are in pdf, set to "single vector" scale factor and "template image" for Render As. Buttons are organized with auto layout and constraints.

Thank you for any suggestions...