Hero Building

I'm trying to make a building be a hero. I copied Blizzard's TD (fake building for placement, replace with non-moving building hero when done). However, my buildings can't seem to gain experience.

When I turn off "Is a building", experience works. When I turn it on, it doesn't. Blizzard's TD has "is a building" on, so I'm missing something.

How do I let my building gain experience?

You can make a hero with no movement and a building model, but no building hero. I believe you can also "build" heroes e.g. if you put Paladin in a peasant's build list, he will be able to "build" a Paladin.

If you don't use a fake placement building, you can build the hero anywhere, even on cliffs (that's what went wrong when I tried that, in any case).

I want "Is a building" set because it affects things like unit selection.

I solved it, I needed to turn on "Building kills give experience"