Abstract: A device for fixing a housing of an electronics module includes an intermediate part (6) on which the housing (1) is fixed, and also includes a rail (5a) for receiving the housing (1) and the intermediate part (6), said intermediate part (6) including a locking element (21) that carries a catch (30) suitable for co-operating with complementary relief on the intermediate part (6) to hold the locking element in a retracted position, from which it is released when the intermediate part (6) and the housing (1) are put into place on the rail (5a).