A drug delivery device comprising a housing body; a piston rod configured to rotate in a rotational direction during dose dispensing under a driving force; and a threaded insert, wherein the piston rod is in threaded engagement with the threaded insert such that during the dose dispensing. the piston rod displaces axially in a distal direction relative to the threaded insert for displacement of a cartridge hung. The threaded insert is movable relative to a stop provided in the housing body and a spring is provided to bias the threaded insert against the stop so that the rotation of the piston rod causes the threaded insert to move away from the stop in response to reaction forces, induced by the cartridge bung into the threaded insert, acting on the piston rod in a proximal direction when the reaction forces exceed a biasing force of the spring.