Punishing someone for a crime before they have committed it is widely considered morally abhorrent. But there is little agreement on what exactly is supposed to be wrong with it. In this paper, I critically evaluate several objections to the permissibility of prepunishment, making points along the way about the connections between time, knowledge, desert, deterrence and duty. I conclude that, although the conditions under which it could permissibly be administered are unlikely ever to arise in practice, nevertheless in principle, nothing is wrong with prepunishment after all.