Are save files cross compatible between Windows and Mac OSX?

[AHALambda]

Ok this is my first thread, please don't be too harsh if I have done something wrong here =/

Ok, I've been playing Penumbra Black Plague on my brother's Windows PC but with the steam sale up I thought I might pick it up for cheap and save him the hassle of me wanting to play games on his PC when he's not using it

The thing is will my save progress so far on the game be able to be carried over to a Mac Steam copy of Penumbra Black Plague? Or will I just need to finish it on his computer?

Thanks for the help guys.