An assembly for a drug delivery device (1) is provided comprising a housing (3), a cartridge holder (2) releasably connectable to the housing (3), a resilient member (10), and an interaction member (14) which is configured to mechanically cooperate with the resilient member (10) and with the cartridge holder (2). The resilient member (10) is configured to rotationally bias the interaction member (14). The assembly has a locked state where the cartridge holder (2) is connected to the housing (3), the cartridge holder (2) being obstructed from movement with respect to the housing (3), and an unlocked state where the connection between the cartridge holder (2) and the housing (3) is released, the cartridge holder (2) being freely moveable with respect to the housing (3). For switching from the unlocked state into the locked state, the cartridge holder (2) is brought into mechanical cooperation with the interaction member (14), the cartridge holder (2) is rotated in a first direction with respect to the housing (3), the interaction member (14) thereby being rotated in the first direction such that the interaction member (14) mechanically cooperates with the resilient member (10) and such that a rotational force exerted on the interaction member (14) by means of the resilient member (10) is overcome for switching the assembly from the unlocked state into the locked state. Furthermore, a drug delivery device (1) is provided.
