A device for locking an adjustable motor vehicle steering column in position, the steering column extending along the longitudinal direction, the locking device including: - a clamp, the clamp comprising first and second flanges (24, 26) spaced apart so as to define therebetween a receiving passage for the steering column, and - a movable cam opposite the clamp, the movable cam being rotatable relative to the clamp, the movable cam comprising at least three non-aligned bosses (46, 48, 50) protruding toward the clamp, and the clamp comprising at least two complementary bosses (32, 34) protruding toward the movable cam, the cam being mounted rotating about a transverse axis (A-A') substantially perpendicular to the longitudinal direction between an unlocked position, in which the bosses (46, 48, 50) do not bear on the complementary bosses (32, 34) and the first and second flanges (24, 26) release the steering column such that the steering column is free to move along the longitudinal direction, and a locked position, in which the bosses (46, 48, 50) bear against the complementary bosses (32, 34) such that the first and second flanges (24, 26) grip the steering column and block its movement along the longitudinal direction, the two complementary bosses (32, 34) having an elongated shape substantially along the vertical direction, the locking device being characterized in that a first complementary boss and a second complementary boss delimits a hollow between them, when the movable cam occupies its unlocked position, a first boss and a second boss are disposed on either side of the first complementary boss, and a third boss is disposed in the hollow, when the movable cam occupies its locked position, the first and second bosses (46, 48) bear against the first complementary boss, and the third boss bears against the second complementary boss. - a clamp, the clamp comprising first and second flanges (24, 26) spaced apart so as to define therebetween a receiving passage for the steering column, and - a movable cam opposite the clamp, the movable cam being rotatable relative to the clamp, the cam being mounted rotating about a transverse axis (A-A') substantially perpendicular to the longitudinal direction between an unlocked position, in which the bosses (46, 48, 50) do not bear on the complementary bosses (32, 34) and the first and second flanges (24, 26) release the steering column such that the steering column is free to move along the longitudinal direction, and a locked position, in which the bosses (46, 48, 50) bear against the complementary bosses (32, 34) such that the first and second flanges (24, 26) grip the steering column and block its movement along the longitudinal direction, the two complementary bosses (32, 34) having an elongated shape substantially along the vertical direction, the locking device being characterized in that a first complementary boss and a second complementary boss delimits a hollow between them, when the movable cam occupies its unlocked position, a first boss and a second boss are disposed on either side of the first complementary boss, and a third boss is disposed in the hollow, when the movable cam occupies its locked position, the first and second bosses (46, 48) bear against the first complementary boss, and the third boss bears against the second complementary boss.