A fastener device (1, 2) for fastening a dispenser member (4) on a reservoir neck (51), the device comprising: a ring (1) forming an annular bearing collar (10) for coming to bear against the top (52) of the neck (51), with a gasket (3) possibly being interposed therebetween, and a skirt (11) including a free bottom end (145) and a deformable fastener section (13) that is deformed by thrust on the free end; and a hoop (2) that surrounds the skirt (11) of the ring (1) and constrains the fastener section (13) to deform inwards into contact with the neck (51); the device being characterized in that the deformable fastener section (13) is separated from the free end (145) by a substantially non-deformable bottom section (14) that is in engagement with the hoop (2).