The present disclosure provides for a drive assembly for a drug delivery device. The drive assembly comprises a housing; a piston rod having a longitudinal axis, a distal end and a proximal end and being axially movable in a distal direction relative to the housing and a mid-body axially fixed inside of the housing and coupled to the piston rod. The mid-body comprises at least one metal ratchet arm configured to prevent the piston rod from moving in the proximal direction. Moreover, a drug delivery device with such a drive assembly is presented.