An assembly of a drug delivery device with a longitudinal axis (L) is given, comprising a body (1) with a proximal end (2) and a distal end (3). The drug delivery device further comprises a drive assembly and a first button member (4). The drive assembly is at least partially arranged within the body (1) and is adapted to facilitate dispense of a medicinal product. The first button member (4) acts on the drive assembly to prepare the drug delivery device for dispensing the medicinal product. The first button member (4) is adapted to be detachable from the body (1) after the preparation of the drug delivery device is completed.