The present invention relates to a luminaire comprising one or more LED light sources (102) arranged within a light chamber that is enclosed by a translucent cover (302), having an inner surface (308), wherein the LED light source (102) is arranged to illuminate the inner surface (308) of the translucent cover (302). The translucent cover (302) comprises a prismatic optical structure (304) on the inner surface (308) for reflecting and/or refracting light from the LED light source (102) omni-directionally. The prismatic optical structure (304) is designed such that a direct view of the LED light source from outside the luminaire is obstructed by means of total internal reflection at the prismatic optical structure.