A fastener for fixing a panel to a support is provided with a snapping-in foot adapted to contract elastically to enter a fixing orifice of the support. The fastener is further provided with a head having a plate, a hub, a shank and a deformable member, the plate and the hub being connected by the shank adapted to be received in a keyhole-shaped groove of the panel formed within the thickness of the panel in which the member and the hub are adapted to be received. The fastener also has a deformable rim including a plurality of arcs and deformable arms, each disposed between one of the arcs and the hub.