Remove navigation bar bottom border on iOS

Hey guys.

I've been using an iOS renderer to remove the border under the navigation bar previously, but for some reason it stopped working.

This is what my old renderer looked like:

[assembly: ExportRenderer(typeof(ContentPage), typeof(NavigationBarRemoveBorderRenderer))]
namespace Namespace.iOS.Renderers
{

    public class NavigationBarRemoveBorderRenderer : PageRenderer
    {

        public NavigationBarRemoveBorderRenderer()
        {

            UINavigationBar.Appearance.ShadowImage = new UIImage();

        }
    }

}

I think it stopped working when I upgraded from Xamarin.Forms 3.0/3.1 to 3.4, but I've tried downgrading all the way back to 3.0, which doesn't fix the problem.

Does anyone have an idea on why this is happening and how I fix it? How do I remove the bottom border on the navigation bar on iOS?