The invention is related to a luminaire for housing a tubular lamp. According to the invention the luminaire has a housing with a light emission window, means for accommodating a tubular lamp in it along the window and in a plane P perpendicular to said window, side reflectores, and lamellae positioned between the reflectors and transverse to the emission window. The lamellae having an outer edge, which is diverging from an inner edge from the plane P towards points A and A' on either side of the plane P. From the point A,A' the outer edge extends towards the nearby side reflector enclosing at point A an angle with the emission window and directed towards the said side reflector.