Drug delivery device comprising a cartridge holder adapted to receive and hold a cartridge in a loaded position, the cartridge holder comprising a distal opening adapted to receive the cartridge. The drug delivery device further comprises an expelling assembly adapted to engage and axially displace a piston in a loaded cartridge to thereby expel a dose of drug from the cartridge, and snap locking means acting on a cartridge being inserted in the cartridge holder, the snap locking means having a locked state in which the cartridge is held in the loaded position and an un-locked state in which the cartridge can be removed from the cartridge holder.
