Getting FontAwesome icons as Titanium Window BackButtonTitle

alloy.js

Alloy.Globals.fontAwesome = require('IconicFont').IconicFont({ 
    font: 'FontAwesome'
});
Alloy.Globals.fontAwesomeBackButton = Alloy.Globals.fontAwesome.icon('icon-chevron-left');

var NappAppearance = require('dk.napp.appearance');
NappAppearance.setGlobalStyling({
    barButton:{
		color:"#ffffff",
		shadowColor: "transparent",
		font:{
			fontFamily: "FontAwesome",
			fontSize:"26dp"
		}
	},
	backButton:{
		backgroundImage:"/images/transparent.png" //this is a transparent image (25x32)
	}
});

app.tss

"Window[platform=ios]": {
    backButtonTitle: Alloy.Globals.fontAwesomeBackButton
}