An anti-theft steering lock for motor vehicles includes an auxiliary safety device for preventing the accidental movement of the latch from its retracted release position to its advanced locking position when the anti-theft device is in the travelling position. The auxiliary safety device comprises an elongate retaining member (13) which is mounted for free rotation about its own axis and the ends (17, 15) of which cooperate respectively with a stop appendage (18) projecting from the latch and a cam surface (16) carried by a rotary operating shaft (4). The retaining member (13) holds the latch in the retracted release position as long as the operating shaft (4) remains in the travelling position. The rotary operating shaft is rotated by turning the key of an associated barrel lock. <IMAGE>