Tabbed page crashing on windows phone

On windows phone when trying to navigate to a tabbed page app is crashing. This code works fine on iOS and Android

            var page = new TabbedPage();
            page.Title = "Practice";
            page.Children.Add(new ListPage("Quiz"));
            page.Children.Add(new ListPage("Test"));
            page.Children.Add(new ListPage("Exam"));
            await Navigation.PushAsync(page);

ListPage is a Content Page containing list. Error: {"Object reference not set to an instance of an object."}
Xamarin.Forms 2.0.0.6490