Vaadin FocusShortcut between button and window

Hi all,
I have a Window class and my normal UI class. In the UI class I have a button which opens a window. Now I want to add shortcuts. ENTER for ButtonClick and DELETE to close the Window. This works so far but I need to click the window with my mouse before the DELTE button works. I tried to solve this problem by adding FocusShortcuts and it works great for the button but it doesn't work for the window. So how can I change the focus from the button to the window with a shortcut?

My UI class code:

protected void init(VaadinRequest vaadinRequest) {
    final VerticalLayout layout = new VerticalLayout();

    Button button = new Button("Orderbuch öffnen");
    button.addClickListener(new ClickListener() {
        public void buttonClick(Button.ClickEvent event) {
            Fenster sub = new Fenster();

            // Add it to the root component
            UI.getCurrent().addWindow(sub);
        }
    });

    // Shortcut to click the button
    button.addShortcutListener(new AbstractField.FocusShortcut(button, KeyCode.B));
    button.setClickShortcut(KeyCode.ENTER);

    layout.addComponents(button);
    layout.setMargin(true);
    layout.setSpacing(true);

    setContent(layout);
}

My window class code:

public class Fenster extends Window {
    public Fenster() {

        // Shortcut to close window
        addShortcutListener(new AbstractField.FocusShortcut(this, KeyCode.F));
        addCloseShortcut(KeyCode.DELETE);

        content.setMargin(true);
        setContent(content);
    }
}

Hi , 

If you try setting focus explicitely to a default component in your window or to the window using setfocus  it should work !