A locking cover for a container having a neck comprising: a cage made from plastic; a body made from plastic, which is fastened around the cage, the body comprising a central orifice; a cap configured to close the central orifice, the cap comprising a flat head to cover the orifice and fastening lugs caught between the cage and the body. Each fastening lug has a breakable zone, and the cap is made from a plastic material, different from the plastic material of the cage and from the plastic material of the body, the plastic material of the cap being chosen to have a resistance to rupture reduced by a dose of gamma irradiation for sterilizing the locking cover.