(Minecraft Beta) Two different kinds of Inc Sacs

There's a bug with inc sacs obtained from villagers (trading):

Inc sacs obtained from villagers can't be used to make dye and the game always  stacks them in a separate slot of my inventory instead of using an existing stack of inc sacs (obtained by killing squids).

I can use the inc sacs from the villagers to dye sheep, but there seems to be no way to get black dye.