The present invention is directed to a drug delivery device with a drive mechanism including a piston rod with a bearing for driving a bung in a cartridge in a distal direction. A movable element is disposed displacably in an axial direction within the drive mechanism. The moveable element is movable between a first position in which a distal end of said movable element protrudes from said bearing and a second position in which a distal end of said movable element lies flush with the distal end of said bearing. The invention is further directed to a method for detecting the contact between the bearing and the movable bung.
