Headlight for a motor vehicle comprising a reflector with an optical axis and at least one focus, a light source placed close to a focus of the reflector, and a transparent optical deviation element placed in front of part of the reflector, this element consisting of a module comprising a so-called "square lens" and the reflector placed behind the said lens, the module being able to provide an essentially horizontal spread of the light. The wall of the reflector comprises at least one scallop on one side of a plane passing through the optical axis of the reflector, and at least one additional reflector is disposed on the side of the scallop opposite to the optical axis, this additional reflector being designed to collect at least some of the light coming from the source emerging from the scallop, and to produce an additional beam which is not intercepted by the lens.