Cannot resolve TargetName for a sub class

 When I add

  <DoubleAnimation  Storyboard.TargetProperty="(ScaleX)" Storyboard.TargetName="ScaleUpper" From="0.2"  To="1" Duration="0:0:7" />

I get the error "Cannot resolve TargetName ScaleUpper".

but the scale transform itself works in the Visual Studio IDE designer, and intelisense picks up the name in the code behind.

<int:Upper x:Name="MyUpper">
    <int:Upper.RenderTransform>
        <ScaleTransform x:Name="ScaleUpper" CenterX="350" ScaleX="1" ScaleY="1" />
    </int:Upper.RenderTransform>
</int:Upper>
 

int is defined xmlns:int="clr-namespace:project1"


what am I doing wrong or is this a bug in Silverlight 2 Beta ...