A dose setting mechanism (202) that prevents dispensing of a drug when an incorrect cartridge assembly (204) is attached to the dose setting mechanism (202). Dispense of a drug may be allowed by preventing rotation of a spindle nut (208) of a drug delivery device (200), and dispense of a drug may be prevented by not preventing rotation of the spindle nut (208). Preventing dispense of a drug may be accomplished by preventing rotation of the spindle (206) when an incorrect cartridge assembly (204) is inserted. Preventing dispense of a drug may be accomplished by preventing the spindle (206) from applying an axial force on the cartridge when an incorrect cartridge assembly (204) is inserted.
