Article dans une revue: Cellini and Lambertini endogenize through a timing game the moves of the central bank and the private sector in a model of monetary policy la Barro and Gordon. They find a multiplicity of equilibria, as the two Stackelberg outcomes emerge as the solutions of the timing game, with different inflation levels. By using the risk-dominance criterion to select the equilibrium we prove that there is a discontinuity in the inflation bias, depending on the inflation aversion of the private sector.