WindowsPhone Landscape NavigationPage shows black area

Hi

I have a strange behaviour in my Xamarin.Forms app on the WinPhone client.
My MainPage is a NavigationPage. And when I navigate to the second page and turn the phone to landscape (also happens on the other way), the page shows a black area on the right side. It seems that the height and width properties don't get re-calculated on the device orientation change.

To reproduce this, just create a new Xamarin.Forms Blank App (Visual Studio 2013 template), Update the Xamarin.Forms nuget to the newest verson (in my case: 2.0.0.6490), and add the following to the App-Constructor:

var second = new ContentPage
{
    BackgroundColor = Color.Green,
    Content = new StackLayout
    {
        VerticalOptions = LayoutOptions.Center,
        Children = {
            new Label {
                XAlign = TextAlignment.Center,
                Text = "Second Page"
            }
        }
    }
};

var button = new Button {Text = "Show Second"};
button.Clicked += async (sender, args) => { await ((NavigationPage) MainPage).PushAsync(second); };

var firstpage = new ContentPage
{
    BackgroundColor = Color.Blue,
    Content = new StackLayout
    {
        VerticalOptions = LayoutOptions.Center,
        Children = {
            new Label {
                XAlign = TextAlignment.Center,
                Text = "First Page"
            },
            button
        }
    }
};

// The root page of your application
MainPage = new NavigationPage(firstpage);

The screenshots in the attachement shows the behaviour.

Is this a bug in Xamarin.Forms? Or miss I just something? Thanks in advance