A brake booster for a brake system of a vehicle, having a first input piston component, and a valve body. The brake booster has a second input piston component, which is pushed away from the first input piston component in the braking direction using a compression spring, and a locking mechanism is embodied such that when the differential travel between the booster travel and the input travel is smaller than a predefined first limit value, the second input piston component is adjustable using the compression spring together with the valve body away from the first input piston component, and when the differential travel exceeds the first limit differential travel, the second input piston component is locked in place on the first input piston component.