The invention relates to a lighting unit (1) having a concave reflector (2) with an axis of symmetry (3) and a light emission window (21) bounded by a circumferential edge (20) transverse to the axis, an elongate light source (30) extending substantially along the axis of symmetry (3), which light source (30) is accommodated in a holder (4) opposite the light emission window (21), and a cup-shaped axially positioned cap (5), which cap partly surrounds the light source and forms an optical screening means to intercept unreflected light rays. According to the invention, the cap (5) is surrounded at a distance d by a screening ring (50), which extends over a height h in the direction of the light emission window (21).