AbsoluteLayout content not filling view

I'm using an AbsoluteLayout to allow for some overlays, but I'm finding that I can't get the content to fill the entire view. My Xaml looks like this:

<AbsoluteLayout BackgroundColor="Yellow">
    <ContentView AbsoluteLayout.LayoutFlags="All" AbsoluteLayout.LayoutBounds="0,0,1,1" BackgroundColor="Black"></ContentView>
</AbsoluteLayout>

I've also tried forcing Padding="0" but that does nothing. Does anyone have an idea what's going on? Is this a bug or am I missing something?