Animating a Border control's width
===

I'm trying to animate a Border control's width in a Windows 8 Metro app. I've managed to animate other properties on the Border, such as Opacity:

    private void Item_Tapped(object sender, RoutedEventArgs e)
    {
        var border = sender as Border;

        var animation = new DoubleAnimation();
        animation.To = 0.0;
        animation.Duration = new Duration(TimeSpan.FromSeconds(1));

        var storyboard = new Storyboard();
        storyboard.Children.Add(animation);

        Storyboard.SetTarget(animation, border);
        Storyboard.SetTargetProperty(animation, "Opacity");

        storyboard.Begin();
    }

But when I try to animate the width of the control:

    private void Item_Tapped(object sender, RoutedEventArgs e)
    {
        var border = sender as Border;

        var animation = new DoubleAnimation();
        animation.To = 600.0;
        animation.Duration = new Duration(TimeSpan.FromSeconds(1));

        var storyboard = new Storyboard();
        storyboard.Children.Add(animation);

        Storyboard.SetTarget(animation, border);
        Storyboard.SetTargetProperty(animation, "Width");

        storyboard.Begin();
    }

Nothing happens.

I am able to do this in WPF, but not in Windows 8. Is this a limitation or bug of Metro, or am I doing something wrong?

Thanks