The present invention relates to a cartridge for a drug delivery device comprising of a container at least partially filled with an injectable medicament, at least one sealing member disposed at a distal end of the container, the sealing member being pierceable by a piercing element for expelling a dose of the medicament, and at least one fixing cap of circular or cylindrical geometry comprising a centric through opening at a distal end face giving access to the sealing member disposed underneath, and comprising at least in sections a structurally strengthened surface structure to keep the sealing member in position and/or to counteract a pressure-induced mechanical deformation of the sealing member, and wherein the distal end face of the fixing cap comprises at least one radially extending corrugation or bead.
