Casting a joined alias in QueryOver loses alias context and looks for property on QueryOver root

If you QueryOver an entity, alias-join to a property on that entity which has an inheritance tree, and then attempt to project a property on a specific subclass of the entity, the property path loses the context of the alias and attempts to find it on the queryover root.

Pseudo code:

QueryOver<Customer>()
.JoinAlias(c => c.Order, () => orderAlias)
.SelectList(list => list.Select( () => ((SpecialOrder)orderAlias).SpecialReason);

blows up.

The equivalent in linq-nhibernate works OK which is why I think this is a bug.
Query<Customer>().Select( c => new { SpecialReason = ((SpecialOrder)c.Order).SpecialReason } );

Will attach issue zip in same format as NH Trunk issues.

Graeme