Making a closet with different wall height than room

[goodmanks]

I have a room with a 10 ' ceiling that contains a closet whose walls only go 8' (imagine box within a box).

I have set the ceiling height of the closet to 8' and set the ceiling height of the enclosing room to 10' but the closet is shown to have walls that go 10'.

What do I have to do to make this work?