The present invention relates to a cartridge holder assembly for a drug delivery device comprising of a cartridge holder adapted to receive a cartridge filled with a medicament to be dispensed by the drug delivery device, wherein the cartridge holder comprises a first through opening at a distal end section to receive a piercing element adapted to penetrate a sealing member of the cartridge, a support structure adjacently arranged to the first through opening and a constriction member arranged between the support structure and a distal end face of the cartridge and having a second through opening smaller than the first through opening.
