A drive unit provided with an end position recognition device includes a radially projecting cam (27) connected to a driveshaft (20) of the drive unit, for reducing the stroke travel of the unit. The radially projecting cam engages, from tooth to tooth, into the inner toothing of a ratchet wheel (110), rotatable about an axis of rotation (111) that is offset and parallel to an axis of the driveshaft (20). The end position recognition device can be retrofitted and is preferably capable of operating even in the case of emergency manual actuation. The cam (27) has a sufficient axial stroke lift such that, in the case of emergency manual actuation, it nonetheless meshes with the ratchet wheel (110) even when the driveshaft (20) is displaced axially.