The reasonable person standard is used in adjudicating claims of self-defence. In US law, an individual may use defensive force if her beliefs that a threat is imminent and that force is required are beliefs that a reasonable person would have. In English law, it is sufficient that beliefs in imminence and necessity are genuinely held; but the reasonableness of so believing is given an evidential role in establishing the genuineness of the beliefs. There is, of course, much contention over how to spell out when, and in virtue of what, such beliefs are reasonable. In this chapter, we identify some distinctive issues that arise when we consider that implicit racial bias might be implicated in the beliefs in imminence and necessity. Considering two prominent interpretations of the reasonable person standard, we argue that neither is acceptable. On one interpretation, we risk unfairness to the defendant-who may non-culpably harbour bias. On another, the standard embeds racist stereotypes. Whilst there are formulations of the defence that may serve to mitigate these problems, we argue that they cannot be avoided in the presence of racist social structures.