A lighting and/or signaling device, for a vehicle, including a light source positioned on a module assembled onto an optical device, the optical device and the module including a first reference mechanism including: at least one slideway mounted on the optical device, the slideway including an interior reference face placed opposite an interior guide face, and at least one extension extending from the module, the extension including a reference bearing face, opposite a contact face, the contact face including at least one contact point. The contact face is configured such that, when the extension has been introduced into the slideway along a direction of introduction, the contact face bears at the contact points against the interior guide face and, locally, at the contact point, the slideway and/or the extension are elastically deformed.