Gamemode corrupt on server restart

Hi guys,
I run a sledbuild server and in my server.cfg I have ‘sv_gamemode sledbuild’ and when I restart the server the gamemode says ‘garrys base’ and you cant do or spawn anything. but when I go to the console and type in, ‘changegamemode slb_sledsnow_v3 sledbuild’ it changes and works, I have tryed adding ‘+gamemode sledbuild’ to the command line too but it just does the same.

Thanks
-Dan