A key and a lock cylinder (10) combination including a key and a lock cylinder having a housing and a plug. The key (25) includes a blade that has a first pin groove (210) on a first lateral side defining a first pin surface, and a second pin groove (215) on the first lateral side defining—a second pin surface. The lock cylinder also includes an auxiliary pin (115) with a first projection (135) defining a first engagement surface engageable by the first pin surface when the key is inserted into the key slot to move the auxiliary pin to a withdrawn position to allow rotation of the plug relative to the housing, and a second projection (140) defining a second engagement surface engageable by the second pin surface when the key is removed from the key slot to move the auxiliary pin to a projecting position to prevent rotation of the plug relative to the housing.