Started a game earlier, my friend was Rome, I was Sparta. I have the DLC, he doesn't. After doing one battle, he always gets booted out to the lobby after my battle.

Is this normal? Has anyone else seen this? I'm suspecting it's because I have DLC, as when I tried hosting it again with the post-battle save, it said something about incompatible versions... if I tried a pre-battle save, it works. But it again boots him out after the battle with my Spartans.