New FormsAppCompatActivity is raising an exception in NavigationRenderer custom renderer

I'm upgrading my app to use FormsAppCompatActivity.

Now in my custom renderer that's inheriting NavigationRenderer, I'm getting an exception when calling base.OnElementChanged:

[MonoDroid] UNHANDLED EXCEPTION:
[MonoDroid] System.InvalidCastException: Cannot cast from source type to destination type.
[MonoDroid] at Xamarin.Forms.Platform.Android.NavigationRenderer.SwitchContentAsync (Xamarin.Forms.Page,bool,bool) <IL 0x000bd, 0x003fe>
[MonoDroid] at Xamarin.Forms.Platform.Android.NavigationRenderer.OnPushAsync (Xamarin.Forms.Page,bool) <IL 0x00004, 0x0003f>
[MonoDroid] at Xamarin.Forms.Platform.Android.NavigationRenderer.PushViewAsync (Xamarin.Forms.Page,bool) <IL 0x00003, 0x00036>
[MonoDroid] at Xamarin.Forms.Platform.Android.NavigationRenderer.<OnElementChanged>b__4_0 (Xamarin.Forms.Page) <IL 0x00003, 0x00033>
[MonoDroid] at Xamarin.Forms.EnumerableExtensions.ForEach<Xamarin.Forms.Page> (System.Collections.Generic.IEnumerable`1<Xamarin.Forms.Page>,System.Action`1<Xamarin.Forms.Page>) <0x000bf>
[MonoDroid] at Xamarin.Forms.Platform.Android.NavigationRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1<Xamarin.Forms.NavigationPage>) <IL 0x000ea, 0x006ff>
[MonoDroid] at Boats.Droid.PageFancyRenderer.OnElementChanged (Xamarin.Forms.Platform.Android.ElementChangedEventArgs`1<Xamarin.Forms.NavigationPage>) [0x00001] in d:\Code\Boats\Droid\Renderers\NavigationPageFancy.cs:33

It's occurring in Xamarin.Forms.Platform.Android.NavigationRenderer.SwitchContentAsync.

I don't exactly what's failing there because I can't step into the source.

The decompiled code for that method is:

using Android.Animation;
using Android.Views;
using System;
using System.Threading.Tasks;

private Task<bool> SwitchContentAsync (Page view, bool animated, bool removed = false)
{
    NavigationRenderer.<>c__DisplayClass13_0 <>c__DisplayClass13_ = new NavigationRenderer.<>c__DisplayClass13_0 ();
    <>c__DisplayClass13_.<>4__this = this;
    base.Context.HideKeyboard (this);
    IVisualElementRenderer renderer = Platform.GetRenderer (view);
    bool flag = renderer != null;
    if (!flag) {
        Platform.SetRenderer (view, renderer = RendererFactory.GetRenderer (view));
    }
    <>c__DisplayClass13_.pageToRemove = this.current;
    NavigationRenderer.<>c__DisplayClass13_0 expr_43 = <>c__DisplayClass13_;
    expr_43.rendererToRemove = ((expr_43.pageToRemove == null) ? null : Platform.GetRenderer (<>c__DisplayClass13_.pageToRemove));
    NavigationRenderer.<>c__DisplayClass13_0 expr_5F = <>c__DisplayClass13_;
    expr_5F.containerToRemove = ((expr_5F.rendererToRemove == null) ? null : ((PageContainer)<>c__DisplayClass13_.rendererToRemove.ViewGroup.Parent));
    PageContainer pageContainer = ((PageContainer)renderer.ViewGroup.Parent) ?? new PageContainer (base.Context, renderer);
    pageContainer.SetWindowBackground ();
    this.current = view;
    ((Platform)base.Element.Platform).NavAnimationInProgress = true;
    <>c__DisplayClass13_.tcs = new TaskCompletionSource<bool> ();
    if (animated) {
        if (NavigationRenderer.currentAnimation != null) {
            NavigationRenderer.currentAnimation.Cancel ();
        }
        if (removed) {
            if (pageContainer.Parent != this) {
                this.AddView (pageContainer, base.Element.LogicalChildren.IndexOf (renderer.Element));
            }
            else {
                ((Page)renderer.Element).SendAppearing ();
            }
            pageContainer.Visibility = ViewStates.Visible;
            if (<>c__DisplayClass13_.containerToRemove != null) {
                Action<Animator> done = delegate (Animator a) {
                    <>c__DisplayClass13_.containerToRemove.Visibility = ViewStates.Gone;
                    <>c__DisplayClass13_.containerToRemove.set_Alpha (1);
                    <>c__DisplayClass13_.containerToRemove.set_ScaleX (1);
                    <>c__DisplayClass13_.containerToRemove.set_ScaleY (1);
                    <>c__DisplayClass13_.<>4__this.RemoveView (<>c__DisplayClass13_.containerToRemove);
                    <>c__DisplayClass13_.tcs.TrySetResult (true);
                    ((Platform)<>c__DisplayClass13_.<>4__this.Element.Platform).NavAnimationInProgress = false;
                    VisualElement element = <>c__DisplayClass13_.rendererToRemove.Element;
                    <>c__DisplayClass13_.rendererToRemove.Dispose ();
                    if (element != null) {
                        Platform.SetRenderer (element, null);
                    }
                };
                NavigationRenderer.currentAnimation = <>c__DisplayClass13_.containerToRemove.Animate ().Alpha (0).ScaleX (0.8).ScaleY (0.8).SetDuration (250).SetListener (new GenericAnimatorListener {
                    OnEnd = delegate (Animator a) {
                        NavigationRenderer.currentAnimation = null;
                        done (a);
                    },
                    OnCancel = done
                });
            }
        }
        else {
            if (pageContainer.Parent != this) {
                this.AddView (pageContainer);
            }
            else {
                ((Page)renderer.Element).SendAppearing ();
            }
            if (flag) {
                base.Element.ForceLayout ();
            }
            pageContainer.set_Alpha (0);
            PageContainer expr_1FA = pageContainer;
            float scaleX;
            expr_1FA.set_ScaleY (scaleX = 0.8);
            expr_1FA.set_ScaleX (scaleX);
            pageContainer.Visibility = ViewStates.Visible;
            NavigationRenderer.currentAnimation = pageContainer.Animate ().Alpha (1).ScaleX (1).ScaleY (1).SetDuration (250).SetListener (new GenericAnimatorListener {
                OnEnd = delegate (Animator a) {
                    if (<>c__DisplayClass13_.containerToRemove != null && <>c__DisplayClass13_.containerToRemove.Handle != IntPtr.Zero) {
                        <>c__DisplayClass13_.containerToRemove.Visibility = ViewStates.Gone;
                        if (<>c__DisplayClass13_.pageToRemove != null) {
                            <>c__DisplayClass13_.pageToRemove.SendDisappearing ();
                        }
                    }
                    NavigationRenderer.currentAnimation = null;
                    <>c__DisplayClass13_.tcs.TrySetResult (true);
                    ((Platform)<>c__DisplayClass13_.<>4__this.Element.Platform).NavAnimationInProgress = false;
                }
            });
        }
    }
    else {
        if (<>c__DisplayClass13_.containerToRemove != null) {
            if (removed) {
                this.RemoveView (<>c__DisplayClass13_.containerToRemove);
            }
            else {
                <>c__DisplayClass13_.containerToRemove.Visibility = ViewStates.Gone;
            }
        }
        if (pageContainer.Parent != this) {
            this.AddView (pageContainer);
        }
        else {
            ((Page)renderer.Element).SendAppearing ();
        }
        if (<>c__DisplayClass13_.containerToRemove != null && !removed) {
            <>c__DisplayClass13_.pageToRemove.SendDisappearing ();
        }
        if (flag) {
            base.Element.ForceLayout ();
        }
        pageContainer.Visibility = ViewStates.Visible;
        <>c__DisplayClass13_.tcs.SetResult (true);
        ((Platform)base.Element.Platform).NavAnimationInProgress = false;
    }
    return <>c__DisplayClass13_.tcs.get_Task ();
}