Using scss @import in my app.scss production doesn't remove comments in final css

In my app.scss file I’m using

@import "./node_modules/bootstrap/scss/bootstrap";

because I’m using (and sometimes changing) some Bootstrap variable into my app.scss.

I found that with ember build -prod it doesn’t remove comments from within bootstrap import in my final app.css.

So in my production css I have this:

 * Bootstrap v4.0.0-beta (
 * Copyright 2011-2017 The Bootstrap Authors
 * Copyright 2011-2017 Twitter, Inc.
 * Licensed under MIT (


How can I remove those superfluous comments?