The light device of a motor vehicle comprises a light unit (4) and a cover (2). The light unit (4) comprises a light guide (7) with a front surface (8) for the exit of light rays (10) from the light guide (7) situated opposite the cover (2), a rear surface (9) comprising unbinding elements (73) configured to reflect light rays (10) towards the front surface (8), and at least one binding surface (71) to bind light rays (10) emitted by the light source (6) associated with the binding surface (71) to the light guide (7). The light device further comprises a carrier (5) situated opposite the rear surface (9) of the light guide (7) and configured to reflect light rays (10) that have escaped from the light guide (7) through the rear surface (9) back to the light guide (7). The cover (2) comprises at least one impermeable region (22) preventing light rays (10) from passing out of the cover (2), and at least one permeable region (21) to allow light rays (10) to pass through the cover (2).