A fan includes: a fan disc; an inter-blade platform including a base and a radial tab, a second orifice being formed in the tab of the platform; and a lock having a downstream edge configured to bear against the tab of the platform. The one among the downstream edge and the yoke of the fan disc includes a pin, the other includes a first orifice, the pin being configured to enter the first orifice and the second orifice so as to block the platform relative to the fan disc.