A gas generator includes an initiator having a case, two electrodes and a cap having a wall delimiting an aperture for insertion of the case, a part delimiting an aperture for access to the electrodes and a retaining part made of plastic material overmolded into the aperture between the initiator, the cap and the part. The wall includes, near the aperture and the protrusion retaining the cap, a second protrusion for supporting the mold in a support direction having a component extending from the bottom toward the aperture, the second protrusion having an outer edge at least partially not covered by the part for use as a support surface in said support direction for a mold to be used for overmolding.