A notorious objection to robust virtue epistemology—the view that an agent knows a proposition if and only if her cognitive success is because of her intellectual virtues—is that it fails to eliminate knowledge-undermining luck. Modest virtue epistemologists agree with robust virtue epistemologists that if someone knows, then her cognitive success must be because of her intellectual virtues, but they think that more is needed for knowledge. More specifically, they introduce independently motivated modal anti-luck principles in their accounts to amend the problem of eliminating luck—this makes their views instances of impure virtue epistemology. The aim of the paper is to argue, firstly, that such a move lacks adequate motivation; secondly, that the resulting impure accounts equally fail to handle knowledge-undermining luck. On a more positive note, these results bolster a more orthodox virtue-theoretic approach to knowledge that assigns a fundamental explanatory role to the notion of ability. In this sense, the paper also sketches an account of ability and a corresponding account of knowledge that explains how success from ability (of the right kind) is incompatible with success from luck.