Trying to get Hammer to use Gmod to test maps

[Artanix]

Alright, so I'm trying to get Hammer to use Garry's Mod to test maps instead of HL2.
So, I went into the "Build Programs" tab in Hammer's config and changed the game executable to "$SteamUserDir\garrysmod\hl2.exe" and the maps dir to "$SteamUserDir\garrysmod\garrysmod\maps".

Then I went ahead and changed the last line in the Run Map dialog to:

$game_exe -game garrysmod +map $file

When I try to run my map I get this in my compile window:

** Executing...
** Command: "d:\steam\steamapps\darkartanix\garrysmod\hl2.exe"
** Parameters: -game garrysmod +map "c1"

But when the game tries to start I just get the valve intro then the game quits out...it doesn't load Garry's Mod. All my parameters seem to be correct...To test, I opened up a command prompt in Windows and put in "d:\steam\steamapps\darkartanix\garrysmod\hl2.exe -game garrysmod +map "c1"" and G Mod came up and loaded the map fine.

Any ideas why it doesn't work from Hammer?