The present invention relates to an assembly for a drug delivery device comprising a proximal end, a distal end and a moveable member, a dose member, a fixed member and coupling means, wherein in a first state, the moveable member is moveable in an axial direction with respect to the fixed member and the dose member and the coupling means retains the dose member to the fixed member, and wherein in a second state of the assembly, the moveable member is permanently connected with the dose member by means of the coupling means and the dose member is released from the fixed member and the assembly is configured to set and dispense a dose of a fluid medicinal product out of an assembled cartridge by movement of the dose member. Furthermore it relates to a method for setting-up a drug delivery device.