Is RowDefinition.Height bindable or not?

The following XAML

<Grid.RowDefinitions>
     <RowDefinition Height="{Binding TopRow}" />
     <RowDefinition Height="*" />
     <RowDefinition Height="100" />
 </Grid.RowDefinitions>

ignores the binding to TopRow. I've tried GridLength, int, double and float as values. The documentation indicates that it should be bindable since it has a static HeightProperty defined. (http://iosapi.xamarin.com/?link=T:Xamarin.Forms.RowDefinition/F) The getter for the property is never called no matter what type I use.

My question is, is it possible to bind Height or not? I do have non-pretty workarounds for this, like setting it by reference in code but it's looks soooo ugly! Image may be NSFW.
Clik here to view.

Thanks

Johan