A method for manufacturing a stopper for closing a neck of a container comprises a first step of molding the stopper in one piece. The stopper includes a sealing membrane provided with a central opening, a tubular stem centered on an axis and extending from the sealing membrane around the central opening, and a capsule connected, by a tear wall, to a free end of the stem. The capsule is configured to be wedged in the stem to seal the neck of the container. The method comprises a second step in which, while the tear wall is intact, a force, in line with the axis, is applied to the stopper so as to break the tear wall and move the capsule inside the stem until the capsule is wedged in the stem.