Results in behavioural economics suggest that material incentives can crowd out motivation if agents are mission-oriented rather than self-interested. We test this prediction on a sample of non-profit organisations in Sweden. Traditionally, contracts with the main principal (the Swedish foreign aid agency) have been based on trust and self-regulation. We designed a randomised policy experiment, effectively replacing the trust-based contract with an increased level of monitoring from the principal. Overall, using both self-reported and observed measures of outreach, we find that the intervention increased outreach, reduced expenditures and reduced the number of financial irregularities.