Android NavigationPage bug: a black bar obscures the lower part of the page

On my Nexus 10 with Android 5.0, there's a problem with NavigationPage's rendering. The same thing happens on an emulator with the same setup.

public class App
    {
        public static Page GetMainPage()
        {
            /*
            //On Android, this renders correctly.
            return new ContentPage
            {
                Content = new BoxView
                {
                    Color = Color.Aqua
                },
            };
             */
            //On Android, this has an extra black bar at the bottom.
            return new NavigationPage(new ContentPage
            {
                Content = new BoxView
                {
                    Color = Color.Aqua
                },
            });
        }
    }