There has been some debate as to whether or not it is possible to keep a promise, and thus fulfil a duty, to supererogate. In this paper, I argue, in agreement with Jason Kawall, that such promises cannot be kept. However, I disagree with Kawall's diagnosis of the problem and provide an alternative account. In the first section, I examine the debate between Kawall and David Heyd, who rejects Kawall's claim that promises to supererogate cannot be kept. I disagree with Heyd's argument, as it fails to get to the heart of the problem Kawall articulates. Kawall's argument however fails to make clear the problem with promising to supererogate because his discussion relies on the plausibility of the following claim: that supererogatory actions cannot also fulfil obligations. I argue that this view is mistaken because there are clear examples of supererogatory actions that also fulfil obligations. In the final section, I give my alternative account of the problem, identifying exactly what is wrong with fulfilling a duty, and thus keeping a promise, to supererogate. My diagnosis emphasises the importance of identifying non-supererogatory actions when it comes to understanding the way in which supererogatory actions go above and beyond the call of duty.