How can I enable DVD or CD Sharing with the Firewall on?

I'm trying to enable "DVD or CD Sharing" in the System Preferences. When I enable it, it says that the Firewall is blocking it. If I go into the Security > Firewall settings, I see that the first item under Advanced... is "DVD or CD Sharing" and that it's set to "Allow incoming connections". If I disable the Firewall completely, it works correctly. Is there any way to get it to work with the Firewall enabled, though?