A main drive shaft brake for a passenger conveyor includes a braking element, an actuator, and a counter-actuator. The actuator is de-energized to release the braking element and halt operation of the passenger conveyor during an abnormal or emergency condition. An energized counter-actuator permits release of the braking element but, when de-energized, inhibits release of the braking element by the actuator to prevent unintentional release of the braking element caused by, for example, an accidental loss of power to the actuator.