FontFamily not working when using TextProperty binding

I'm using my own font-family to display icons on xamarin forms. I'm having issues when I use text binding:

this works:
<Label FontFamily="{StaticResource ascendantIconFontFamily}" Text="&#xe901;"></Label>

This doesn't work:
<Label FontFamily="{StaticResource ascendantIconFontFamily}" Text="{Binding IconFontCode}"></Label>

Any idea?

Thanks