How to access window.opener while using gwt.jsinterop

Question

I want to access the javascript window.opener via gwt.jsinterop. So i defined my interface like this:

@JsType(isNative=true, namespace=JsPackage.GLOBAL, name="window")
public class Window {
    @JsProperty
    public static native Window getOpener();
}

But this does not work. It seems i have to define:

@JsType(isNative=true, namespace=JsPackage.GLOBAL)
public class Window {
    @JsProperty
    public native Window getOpener();
}

But how can i access the basic instance "window" of "Window"? (See different case)

Thanks