The disclosure refers to a cap assembly for covering a needle shield of an injection device, the cap assembly comprising: a collar, and a cap with a sheath and a bottom, wherein the collar is movable along a longitudinal direction relative to the sheath from an unlocked position not engaging the sheath towards a locked position, force-lockingly engaging the sheath, thereby locking the sheath to the needle shield.L'invention se rapporte à un ensemble de coiffe pour recouvrir une protection d'aiguille (3) d'un dispositif d'injection, l'ensemble de coiffe comprenant : - un collier (1, 11), - une coiffe (2, 12) avec une gaine (2.1, 12.1) et un fond (2.2, 12.2).
