RibbonWindow set MinWidth or MinHeight

Hello,

  When RibbonWindow set MinWidth or MinHeight,
  if width or height to be smaller than MinWidth or MinHeight,
  it's clipping the window, but previous version is ok.

  The simple example :

  <Grid>
      <Button VerticalAlignment="Center" Height="100" Background="Yellow">Test</Button>
  </Grid>

  public partial class MainWindow : RadRibbonWindow
  {
      public MainWindow()
      {
          InitializeComponent();

          this.MinWidth = 500;
      }
  }

  2015 Q1 is OK
  2015 Q1 Hotfix 0316 is OK
  2015 Q1 Hotfix 0323 is clip
  2015 Q1 SP1 is clip
  2015 Q1 SP1 Hotfix 0406 is clip
  2015 Q1 SP1 Hotfix 0413 is clip

  How can I fix this ? Thanks.

Regards