WPF - can only be based on style with a target type which is the base type

This is sending me nuts, mostly because it works great while running (the problem only occurs during development), but I decided to ask anyway how am I working on a large project and I want to best implement things.

First, I have a component from the third part library, it is basically like a border, and it is defined this way (with F12):

public class AdvancedBorder : ContentControl

      

        
        
        
      

    

I love the visual aspect of this thing, but I need to add some functionality. So I created a new user control:

public class SelectableCard : AdvancedBorder
{
    // bunch of custom properties and stuff

    static SelectableCard()
    {
        DefaultStyleKeyProperty.OverrideMetadata(typeof(SelectableCard), new FrameworkPropertyMetadata(typeof(SelectableCard)));
    }
}

      

        
        
        
      

    

Finally, I need to keep exactly the same visibility, but add some triggers, so I put this in generic.xaml:

<Style TargetType="{x:Type customControls:SelectableCard}" BasedOn="{StaticResource ResourceKey={x:Type otherLibrary:AdvancedBorder}}">
    <Setter Property="HorizontalAlignment" Value="Stretch"/>
    <Setter Property="VerticalAlignment" Value="Stretch"/>
    <Style.Triggers>
        <Trigger Property="customControls:SelectableCard.IsSelected" Value="True">
            <Setter Property="Background" Value="{DynamicResource MyLightBrush}" />
        </Trigger>
    </Style.Triggers>
</Style>

      

        
        
        
      

    

customControls

is xmlns for my namespace, otherLibrary

is xmlns for third part library.

Everything works fine at runtime and doesn't give any errors. During development I get no errors with generic.xaml, but as soon as I put the SelectableCard in some xaml file I get

Can only be based on target type style, which is the base SelectableCard type

And I don't get it at all, especially since it works at runtime. I can remove the attribute BasedOn

and I don't get any more complaints during development, but then I need to add an installer for the template, otherwise I can't see anything at runtime.

What am I doing wrong, here?