ActiveWindow not Updated whith hosted WinForms-Control in floating window

When hosting a Windows Forms Control inside a WPF DockSite window, the ActiveWindow (and also LastActiveXXXWindow) is not updated properly for floating windows.

Sample:

<Window x:Class="WpfApplication7.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:docking="http://schemas.actiprosoftware.com/winfx/xaml/docking"
        xmlns:forms="clr-namespace:System.Windows.Forms;assembly=System.Windows.Forms"
        Title="MainWindow" Height="350" Width="525">
    <docking:DockSite>
        <docking:Workspace>
            <docking:TabbedMdiHost>
                <docking:TabbedMdiContainer>
                    <docking:DocumentWindow Title="Forms" CanRaft="True">
                        <WindowsFormsHost>
                            <forms:TextBox />
                        </WindowsFormsHost>
                    </docking:DocumentWindow>
                    <docking:DocumentWindow Title="WPF" CanRaft="True">
                        <TextBox />
                    </docking:DocumentWindow>
                </docking:TabbedMdiContainer>
            </docking:TabbedMdiHost>
        </docking:Workspace>
    </docking:DockSite>
</Window>

 To reproduce:

1. Start the application and attach Snoop, to check the actual values for ActiveWindow and LastActiveXXXWindow.
2. Make the document window "Forms" floating.
3. Now switch between the document window "WPF" within the main window and the floating window "Forms" and watch the ActiveWindow and LastActiveXXXWindow properties.

-> In both cases the ActiveWindow and LastActiveDocumentWindow is the "WPF"-window.

Is there a way to get those properties (and the associated events) work in this case?

Thanks in advance

Stefan