Blocks Styles Support

Hello,

I am developing a child theme with GP and I am missing block styles.
This doesn't show the styles selection box in Gutenberg:

const { registerBlockStyle } = wp.blocks;
const { __ } = wp.i18n;

registerBlockStyle('generateblocks/headline', {
    name: 'kara-fancy-centered',
    label: __('Kara centered', 'kara'),
    isDefault: true
});