A device for blocking the turnability of the steering spindle 3 of a motor vehicle contains a movable interlocking element 14 that is situated in a lock chamber 12 and engages into the steering spindle 3 in its locked position, as well as an actuating device 9 for actuating the interlocking element 14. This device is characterized by the fact that the lock chamber 12 is passively secured against manipulative access by electric/electronic operating components K required for driving the motor vehicle. This is realized by arranging these operating components K in such a position relative to the lock chamber 12 that the function of at least one operating component K is terminated if manipulative access is attempted.