Layout transform not working

Hi,

I'm in the process of applying the theming on my application and I encounter an issue. Minimalistic application:

<Window x:Class="WpfApplication2.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" Height="350" Width="525">
    <Grid>
		<Expander Grid.Column="0" ExpandDirection="Right">
			<Expander.Header>
				<TextBlock Text="Conditions">
					<TextBlock.LayoutTransform>
						<RotateTransform Angle="-90"/>
					</TextBlock.LayoutTransform>
				</TextBlock>
			</Expander.Header>
		</Expander>
	</Grid>
</Window>

 and in code behind:

namespace WpfApplication2
{
	/// <summary>
	/// Interaction logic for MainWindow.xaml
	/// </summary>
	public partial class MainWindow : Window
	{
		public MainWindow()
		{
			ActiproSoftware.Windows.Themes.ThemeManager.AreNativeThemesEnabled = true;
			InitializeComponent();
		}
	}
}

 The text ends up upside down. If the 'AreNativeThemesEnabled' line is commented out you can see what the result should be.

Anyone knows how this can be fixed?

many thanks,

Bruno