How to clear the Navigation Stack in a Xamarin.Forms 4.0+ Shell app?

I like to remove all pages from the navigation stack and make my current page the new root page. How can I do that?
Whole navigation is done with the new Shell navigation (calling Shell.GoToAsync(route) or the Flyout Menu).
I tried collecting the current stack from Shell.Current.CurrentItem.Navigation.NavigationStack and Shell.Current.Navigation.NavigationStack , but the only element in there is null for any reason.
I am using the latest Xamarin 4.2.848062 version.