An assembly for a medication delivery device (1) is described comprising a body (3), a piston rod (4) adapted and arranged to be rotated with respect to the body (3) for setting a dose of a medication (10) and to be axially moved in a distal direction with respect to the body (3) for delivering the set dose of the medication (10), wherein, as seen in cross-sect ion, the piston rod (4) comprises a plurality of ratchet teeth (24) adapted and arranged to enable rotation of the piston rod (4) during setting of a dose of the medication (10), and at least one stop member (18) secured against axial and rotational movement with respect to the body (3), wherein the stop member (18) is adapted and arranged to mechanically cooperate with the piston rod (4), wherein when setting the dose of the medication (10), the piston rod (4) becomes aligned with the stop member (18), wherein when delivering the set dose, the piston rod (4) is moved in the distal direction towards the stop member (18) such that the piston rod (4) and the stop member (18) abut at the end of the dose delivery operation and such that further distal movement of the piston rod (4) is prevented after the set dose of the medication (10) was delivered. Furthermore, a medication delivery device (1) comprising the assembly is described.L'invention concerne un ensemble pour un dispositif de distribution de médicament (1) comprenant un corps (3), une tige de piston (4) conçue et agencée pour être tournée par rapport au corps (3) pour régler une dose d'un médicament (10) et pour être déplacé axialement dans une direction distale par rapport au corps (3) pour délivrer la dose réglée du médicament (10), dans lequel, comme vu en coupe transversale, la tige de piston (4) comprend une pluralité de dents d'encliquetage (24) conçu et agencé pour permettre la rotation de la tige de piston (4) pendant le réglage d'une dose du médicament (10), et au moins un élément d'arrêt (18) fixé contre un mouvement axial et rotationnel par r
