Résumé : This paper explores the effects of anti-corruption sensitisation messages on bribe-taking and public service delivery. In a novel lab-in-the-field experiment in Burundi, 527 public servants were asked to allocate rationed vouchers between anonymous citizens; some of these citizens attempted to bribe the public servants to obtain more vouchers than entitled. Two groups of public servants were randomly exposed to similar short messages that called to either the idea of good governance or professional values of integrity. Public servants exposed to the professional identity message behaved in a more equitable manner than those not exposed to any message. We hypothesise that reflecting upon professional values increases moral costs and prompts fairer service delivery. Bribe-taking was not impacted by the messages and bribe-taking and service delivery appear to be distinct dimensions, correlated to different variables. The experiment provides new insights into the design of public service improvement and anti-corruption strategies.