A luminaire (20) comprising a light guide (11) having a first refractive index (n1), the light guide (11) comprising a light-entry surface (14), a light-reflecting surface (15) for reflecting light entering at the light-entry surface (14), and a light-exit surface (16) opposite the light-reflecting surface (15), for allowing light to exit from the light guide (11), the light guide (11) being tapered toward the opposite end relative the light-entry surface (14). The luminaire (20) further comprises a light source (13), arranged to emit light toward the light-entry surface (14); a first optical member (17), having a second refractive index (n2), in optical contact with the light-exit surface (16) of the light guide (11); a second optical member (18), having a third refractive index (n3), in optical contact with the light-reflecting surface (15) of the light guide (11); and a functionality-enhancing structure (19) arranged on the opposite side of the second optical member (18) in relation to the light guide (11), for affecting an optical property of the luminaire (20) when the light source is in an off-state. The first refractive index (n1) is greater than each of the second (n2), and third (n3) refractive indices, and the second refractive index (n2) is greater than the third refractive index (n3).