Ernest Sosa has argued that if someone knows that p, then his belief that p is “safe”. and Timothy Williamson has agreed. In this paper I argue that safety, as defined by Sosa, is not a necessary condition on knowledge – that we can have unsafe knowledge. I present Sosa’s definition of safety and a counterexample to it as a necessary condition on knowledge. I also argue that Sosa’s most recent refinements to the notion of safety don’t help him to avoid the counterexample. I consider three replies on behalf of the defender of safety, and find them all wanting. Finally, I offer a tentative diagnosis of my counterexample.