[Zope] ZCatalog'ing nested ZClasses?

I have a nested ZClass (Foo2) in a folderish container class (Foo1), ie., Foo1Product Foo1Class Foo2Class My problem is that Foo2Class's meta-type does not appear in a ZCatalog instance's "Find items to ZCatalog" selection box. This is true even if the ZCatalog is created inside a Foo1Class instance. However, if I select "All types" in "Items to catalog", Foo2Class instances *are* found and catalogued. How can I get this nested ZClass to show up in the selection box? Cheers, Darran.