The present invention relates to a locking mechanism for a medicament delivery device comprising, a housing (12), a locking member (96) having a flexible lever (102) configured to be in a non-activated position and an activated position, a pinion gear (94) connected to the locking member, a rotatable secondary dose member (90) exerting a biasing force on the lever in the non-activated position and releasing the biasing force in the activated position, and a lead screw member (58) biased to slide in a distal direction and having an annular ledge 62 that engages the lever in the non-activated position preventing axial movement of the lead screw, wherein the lead screw slides distally when the lever becomes disengaged from the ledge in the activated position when rotation of the pinion rotates the secondary dose member moving the lever from the non-activated to the activated position.
