How do borrowers respond to improvements a lender’s ability to punish defaulters? We implemented a randomized field experiment in Malawi examining the impact of fingerprinting of borrowers, which improves the lender’s ability to withhold future loans from individuals who have previously defaulted. Study participants were smallholder farmers applying for agricultural input loans, and were randomly allocated to either: 1) a control group, or 2) a treatment group that was fingerprinted as part of the loan application. Both treatment and control groups were given a presentation on the importance of credit history in ensuring future access to credit. For the subgroup of farmers with the highest ex ante default risk, fingerprinting led to substantially higher repayment rates. By contrast, fingerprinting had no impact on repayment for farmers with low ex ante default risk. Higher repayment for the high-default-risk subgroup is due to reductions in adverse selection (smaller loan sizes) and lower moral hazard (more intensive input application yielding higher farm profits).