A tradition in political economy holds that constitutions should be designed under the assumption that politicians are knaves. A criticism of this position says that a constitution so designed will cause political actors to behave worse than they otherwise would. Designing a constitution for knaves creates knaves. I critique this argument in the current paper. I advance two claims. First, all constitutions create knaves, because the activity of politics itself creates knaves. Second, knavish constitutions better cultivate virtue when compared to constitutions that lack knavish constraints and guardrails. Put together, the two arguments imply the criticism has it exactly backwards: if you want virtuous politicians, design constitutions under the assumption that they are knaves.