People give surprising weight to others’ expectations about their behaviour. I argue the practice of conforming to others’ expectations is ethically well-grounded. A special class of ‘reasonable expectations’ can create prima facie obligations even in cases where the expectations arise from contingent pre-existing practices, and the duty-bearer has not created them, or directly benefited from them. The obligation arises because of the substantial goods that follow from such conformity—goods capable of being endorsed from many different ethical perspectives and implicating key moral factors such as consent, fairness, respect, autonomy, and reciprocity. Given the innumerable situations where such expectations can arise, their ethical significance is critical both practically and philosophically.