After hook not setting property?

[zbuttons]

Hello!
I am using ExpressMapper and I can't get it to work with custom property.
I am doing the following:

ExpressMapper.Mapper.Register(Of Class1, Class2)().After(Function(x, y) y.specialProperty = "test")
ExpressMapper.Mapper.Map(Of List(Of Class1), List(Of Class2))(list)

and in the list(Of Class2) I get back, the items do not have specialProperty set.

What am I doing wrong?