An arrangement (100) for a drug delivery device (200) is provided. The arrangement comprises a cap (1) defining a cavity (9) and a body (2), wherein the cap (1) or the body (2) comprise a recess (5), wherein the cap (1) or the body (2) is provided with a seal (11) further comprising a sealing surface (12). When the cap (1) is attached, the sealing surface (12) of the seal (11) seals a section (10) of the cavity (9). When the cap (1) is detached from the body (2), either the recess (5) is moved towards the side of the seal (11) which faces the section (10) of the cavity (9) or the seal (11) is moved towards the side of the recess (5) which faces the section of the cavity (9), and when either at least a part of the recess (5) has passed the sealing surface (12) or, when the sealing surface (12) has passed at least a part of the recess (5), this part of the recess (5) establishes a passageway (17) between the cavity (9) and the environment.
