I argue that false propositions play two important roles in epistemology: we can be justified in believing them, and they can justify us in believing further propositions. Some philosophers have recently argued, against the first claim, that it ignores the distinction between justification and excuses. But there is no good argument from that distinction to the claim that we cannot be justified in believing falsehoods. I offer two arguments in favor of the second claim: one regarding the proper solution to the problem of easy knowledge, and the other regarding our justification in certain cases of rational mistakes.