AllowedTypes not working with a marker interface inheriting from IContentData

Description

Steps to reproduce

1. Create an Interface.

   public interface IFoo : IContentData { }

2. Create a UIDescriptor.

   [UIDescriptorRegistration]

   public class IFooUIDescriptor : UIDescriptor<IFoo> { }

3. Create a block that implements the interface.

   [ContentType(GUID = "EB67A99A-E239-41B8-9C59-20EAA5936047")]

   public class FooBlock : BlockData, IFoo { }

4. Add a ContentReference property with the AllowedTypes attribute to a page.
5. Run the Alloy website in CMS edit mode.
6. Go to the page where you added the new ContentReference property.
7. Try to add a content reference by clicking on the property.
8. ContentReference is not showing any content but Root.