Bug in Rendering text color in xaml when involving a command. (iOS only)

I'm writing in Xamarin forms, and when I define a TextColor property on a Button, and a command, then the color I defined is overridden in iOS and the default color is used.

This is the button I'm trying to change it's text color:

When I removed the Command="{Binding Signin}", then the text color was black..

I'm using the latest stable Xamarin.iOS.
The device I checked on is a iOS simulator.

Thanks in advance,
Ido