A drive assembly (180) for a drug delivery device (101) is provided, the drive assembly (180) comprising a spring member (127), a piston rod (102) and a piston rod nut (126) being engaged with the piston rod (102). The piston rod nut (126) is configured to rotate and axially move during a setting of a dose, wherein the spring member (127) is compressed when the piston rod nut (126) is moved during the setting of a dose, and wherein the piston rod nut (126) is rotationally fixed during a dispense of a dose.
