Sass in Laravel 5.4

In Laravel < 5.4 I was able to do the following with elixir to compile all of my sass files in one css file.

mix.sass([
    'file_1.scss',
    'file_2.scss',
    'file_n.scss'
], 'public/css/app.css');

In Laravel 5.4 this is not working. Is there a chance to do something similar in Laravel 5.4?

via Chebli Mohamed