A locking device which has a lock cylinder and a matching key. The key has a key bit with at least one coding notch and a blocking rib with at least one indentation. The lock cylinder has a housing with a bearing bore and a cylinder core that is mounted in the bearing bore and a blocking member. The blocking member is engagable in a blocking recess of the bearing bore and prevents rotation of the cylinder core. A pivot lever is mounted in the cylinder core and has a bearing end about which the pivot lever pivots, and a sensing end which senses the blocking rib The pivot lever closes off a capturing opening for the housing pin when the blocking rib is the proper height and opens the capturing opening after a partial rotation of the cylinder core when the blocking rib is missing.