On a common characterization, moral luck occurs when factors beyond agents' control affect their moral responsibility. The existence of moral luck is widely contested, however. In this paper, I present a new challenge for deniers of moral luck. It seems that some factors beyond agents’ control – such as moral principles about blame- and praiseworthiness – clearly affect moral responsibility. Thus, moral luck deniers face a dialectical burden that has so far gone unnoticed. They must either point to a relevant difference between factors like moral principles and the kind of factors that according to them do not affect moral responsibility or show how they can avoid having to point to such a difference. I argue that no obvious way to meet the...