Is_Planet_Domed not working?

So, I was experimenting a bit today and tried out an idea. I wanted to make facilities cost twice as much (to build and maintain) if the planet is domed. Seems easy, right? IN facilities.txt, just use something like this:

Cost Minerals Formula := ( 1000 + ( ( [%Level%] - 1 ) * 50 ) ) * iif( Is_Planet_Domed(), 2, 1 )

Cost Radioactives Formula := ( 1000 + ( ( [%Level%] - 1 ) * 50 ) ) * iif( Is_Planet_Domed(), 2, 1 )


Wrong.

Whether the facility is built on a domed or undomed planet, the cost is as if the Is_Planet_Domed is ALWAYS returning false.

Is there something else I need to do? Has anyone else tested Is_Planet_Domed()?