Notification pop-ups not darkened

[Olddddd]

Hello there,

Don't know if it's a bug or a feature request, but the notification pop-ups are not darkened, is that normal?

In case ShadowFox doesn't cover it, I also saw a Reddit's post mentioning adding this code to the userChrome.css file but it doesn't work:

@-moz-document url("chrome://global/content/alerts/alert.xul"){ #alertBox{ background-color: black !important;; color: white !important; } }

Any thoughts?

Thanks.