NUI + Custom font. Text are cut by half

I use NUI ( https://github.com/tombenner/nui ) and I want to display text in button with certain font and size. Here is my 'css' file:

accessoryButton {
    font-name: GothamSSm-Light;
    font-size: 20;
    font-color: white;
}

And what I get from it (screenshot with blended layers):

.

And it happens not only with button, I tried the same on UITextField - same result. If I change font-name on Arial, for example, text appears correctly. I've checked that font on test project without NUI, it works fine.