the invention relates to a locking cap made of a molded plastic material for a vessel having a neck , intended for blocking a stopper in said neck , including a wire - cap adapted for surrounding the stopper and the neck in the mounted configuration of the cap . the wire - cap includes first and second flexible tabs capable of being respectively blocked on the neck and on the stopper , said first tabs being offset relative to said second tabs in an axial direction relative to said neck . the cap also includes a ring surrounding the wire - cap for preventing access to said tabs from outside the ring . the ring and the wire - cap are designed so as to be fitted and locked together . the tabs of the wire - cap are respectively arranged at an angle in first and second openings which are formed by the mesh of the wire - cap , and in which the tabs can disappear when mounting the cap on the neck .