An assembly for a drug delivery device is provided comprising a housing, a cartridge holder releasably connectable to the housing, a resilient member, and an interaction member which is configured to mechanically cooperate with the resilient member and with the cartridge holder. The resilient member is configured to rotationally bias the interaction member. The assembly has a locked state where the cartridge holder is connected to the housing, the cartridge holder being obstructed from movement with respect to the housing, and an unlocked state where the connection between the cartridge holder and the housing is released, the cartridge holder being freely moveable with respect to the housing.
