A fluid regulator includes an actuator, a body assembly, and a balancing system disposed between the actuator assembly and the body assembly. The actuator assembly includes an upper casing, a lower casing secured to the upper casing, and a diaphragm assembly disposed between the upper and lower casings. The body assembly includes a stem assembly operatively connected to the diaphragm assembly to move with the diaphragm assembly. The balancing system includes a diaphragm operatively connected to the stem assembly to move with the stem assembly. The lower casing of the actuator assembly includes a wall defining a portion of a balancing cavity that receives the balancing system and an inner surface that ends at a shoulder and has an annular groove formed therein that receives a portion of the diaphragm as the fluid regulator moves from a fully open position to a lockup position.