The present disclosure relates to a socket for an electric bulb, formed by a tubular body having two longitudinal cavities for receiving contacts crimped onto cables, said tubular body including lateral clip-fastening elements having lugs for locking into the base of a motor vehicle light or headlight. The disclosure provides that the locking elements are provided with internal shoulders having dimensions and positions configured such as: to be engaged behind a transverse surface of the contact when said contact is correctly mounted and to allow insertion into the base of the light or headlight when the clip-fastening elements are biased; and to prevent the movement of the elements which would allow insertion of the socket when the contact has not been correctly engaged.