Inspired in part by a renewed attention to Aristotle's moral philosophy, philosophers have acknowledged the important role of the emotions in morality. Nonetheless, precisely how emotions matter to morality has remained contentious. Aristotelians claim that moral virtue is constituted by correct action and correct emotion. But Kantians seem to require solely that agents do morally correct actions out of respect for the moral law. There is a crucial philosophical disagreement between the Aristotelian and Kantian moral outlooks: namely, is feeling the correct emotions necessary to virtue or is it an optional extra, which is permitted but not required. I argue that there are good reasons for siding with the Aristotelians: virtuous agents must experience the emotions appropriate to their situations. Moral virtue requires a change of heart.