A locking mechanism (18) for a belt reel (10) of a belt retractor in a vehicle, including a carrier (22) coupled to the belt reel (10) of the belt retractor, an inertia mass (24) which is pivoting to a limited extent relative to the carrier (22) and a leaf spring (28) applying the inertia mass (24) in a home position, includes at each of the carrier (22) and the inertia mass (24) a seat (34, 36) for the spring ends (30, 32) of the leaf spring (28) in which the spring ends (30, 32) of the leaf spring (28) are pivoted to a limited extent.