Xamarin Carouselview throws invalidcastexception

Based on the example I found here: https://blog.xamarin.com/xamarin-forms-4-0-feature-preview-an-entirely-new-point-of-collectionview/

I decided to implement a Carouselview, but it gives me an exception invalidcastexception
I also added global::Xamarin.Forms.Forms.SetFlags("Shell_Experimental", "Visual_Experimental", "CollectionView_Experimental"); in my MainActivity for Android.

Any idea what's wrong?

I created a git-repo. You can find it here