Problem with GIMP - Alpha channels exported as white instead of black

[La Grandmaster]

For some reason gimp has started saving alpha channels as plain white (instead of plain black), this is causing problems when I try to use alpha channels in game, as I believe M&B requires alpha channels to be plain black. Anyone experienced this problem before, I have had a search and found no info on it so far. It happens when I export files as png and as dds.

EDIT: In fact white alpha channels still seam to work, although I am worried they will cause some problems with shaders. It is really confusing me

 

[produno]

Im pretty sure you can change it via settings in gimp, though im not sure where and im not at my computer atm. So not much help really!