An arrangement for locking the steering shaft of a motor vehicle, includes a blocking device and a toothed ring which is arranged on the steering shaft and in which a blocking element, which is arranged so that it can be displaced from an unlocked position into a locked position, of the blocking device engages. To allow the blocking device to be attached to the steering device of the vehicle in question and exchanged in a simple manner and to ensure that the blocking device cannot be removed in the locked state of the blocking element, the blocking device, which is provided with a housing, is releasably connected to a flange, which is attached to the steering device, via an adapter part. The flange has a recess which is designed in such a manner that the adapter part, for fitting of the blocking device, can be inserted in a partial area of the recess and can then be displaced along a guide into its limit position. Moreover, transverse webs are arranged between the teeth of the toothed ring, which webs, in the locked position of the blocking element, prevent axial displacement of the adapter part along the recess in the flange to the partial area.