A lamp socket assembly for an automotive headlamp, wherein a mount is formed at the back of the headlamp reflector. A socket fixture is screwed to the reflector at a rear surface of the lamp. The mount has a plurality of partial circumferential depressions. The socket fixture has corresponding cuts about its central hole. However, the cuts extend over only a portion of the depressions. A lamp has an integral socket with a focal point plate having a plurality of radially extending tongues. The tongues can be inserted through the cuts into the depressions and be engaged therein. In a dual lamp unit, one of the depressions of the mount for the auxiliary lamp can have a protrusion not present in the main lamp. The tongues for the main and auxiliary lamp sockets differ so that the main lamp socket cannot be engaged with the mount for the auxiliary lamp.