The invention relates to a lock for a motor vehicle, comprising an external actuating lever (2), an inertial element (3), and a detent lever (4) which is preloaded by a spring element (6) and rotatably mounted on the inertial element (3), wherein said detent lever (4) is able to cooperate with a blocking contour arranged on a housing of the lock, wherein the external actuating lever (2) acts directly on the detent lever (4) and wherein a movement of the external actuating lever (2) can be blocked by an inertia of the inertial element (3) and the external actuating lever (2) cooperates with the detent lever (4) by way of a control contour (9).