External font not applied by CSS - javafx-8

Question

I'm trying to create icon buttons. I've downloaded them from flaticon.com and had them exported as icon font files, which includes a TTF file.
In my css file I specify the external font as:
#font-face {
font-family: flaticon;
src: url('/flaticon/flaticon.ttf');
}
I've defined a button class that should use this font as follows:
.flaticon-button {
-fx-font-size: 90px;
-fx-font-family: flaticon;
-fx-padding: 10px;
}
My code applies the styleclass as follows:
Button button = new Button("\ue000");
button.getStyleClass().add("flaticon-button");
But unfortunately it doesn't show the expected icon.
When I load the font in my code and set it explicitly the correct icon is shown:
Font font = Font.loadFont(this.getClass().getResource("/flaticon/flaticon.ttf").toExternalForm() , 90d);
Button button = new Button("\ue000");
button.setFont(font);
I'm obviously overlooking something small, but despite how many examples I browse on the internet, or how long I stare at Oracle's CSS documentation I can't see what.
So, what is wrong with my CSS declaration and usage?

Answer 1

Thanks to the comment of rossum, I realized it it might have something to do with the URL not resolving to the class, as Class.getResource() does.
By loading the font in the main, before it is references by the code, it seems to be resolved. I guess there is no other way, but it seems to be a bit of a hack to me.