This is a tough riddle, a man must say one thing to save his life.?

A man's ship sinks, so he escapes with a small row-boat. He lands on an island, on which the inhabitants are cannibals. He was taken to the chief, wehre he was told that he could say 1 last thing. The chief tells him that if what he says is a lie, he is boiled in oil. If it is the truth, he is boiled in water. What does he say, in order to spare his life?