Layout transform not working

<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>

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