two female ferrets fighting

I have a 3 year old ferret, Kenya, and a 1 year old Female, baby, who, when put together seem to want to rip each other's face off. They get along fine at first; they sniff each other a bit, but then when they come face to face, start hissing, and then attack each other. I want to keep them in the same cage, but they don't get along! What do I do? I don't want them to kill each other!