Can't bind Enter key in HL2 Deathmatch

[kilky]

I'm using Linux Mint 14 x64 and I'm playing HL2 DM for the first time. I never got to try it out back in the day. I'm finding that I can't bind the Enter key to Jump, or anything else. I always use Enter to jump and I know this has worked in other Source engine games on Linux/Windows. Is there a workaround or fix coming?