An assembly for mounting a visor on a helmet includes a visor assembly having a lens and a fastening element with a pair of latching prongs each with a resiliently displaceable prong end; a casing attached to the helmet and having a pair of channels each for receiving the a latching prong and a pair of fixtures, each fixture for engaging a respective prong end when displaced outwardly; and a lock having a pair of locking prongs, each locking prong being insertable into one channel from an opposite end as the latching prongs and each locking prong having a locking prong end that is positionable under a respective latching prong to prevent displacement of the latching prong end inwardly to disengage from the respective fixture.