Console Command for Altering Game Difficulty?

Not sure whether this is the correct section for asking questions related to console commands.

There is a console command for altering game difficulty in mid game, but I know not how to use it correctly because I don’t know what to use for the argument:

game_difficulty [???]

I’ve tried the following to increase the difficulty in one of my saved games from Veteran to Legendary, without success:

game_difficulty legendary
game_difficulty legend
game_difficulty hell
game_difficulty nightmare
game_difficulty 3
game_difficulty impossible
game_difficulty pandora

But none of them works. If anyone here know the correct command, please post here. Thank you.

game_difficulty veryhard