Room bounded by future walls??

[archerin]

I moved tenant finish out of one floor to a future phase. But when I try to place a room in the now-empty floor, it still recognizes the walls which haven't been built yet. There are no room separation lines, nor are the walls on the floor below the same shape, so I know it's not somehow seeing those. It doesn't matter if I make a new room or use an old room, and it happens all over the floor - a room I try to place will fill up one of the future rooms.

Any tricks for getting the room to fill the whole floor?

Thanks!