A circuit breaker is provided with a current-limiting fuse mounted in a removable fuse holder and electrically connected in series with the circuit breaker contacts. A self-biasing mechanical interlock member prevents insertion or removal of the fuse unless an operating lever is in the OFF position. An indicator lamp is connected across the fuse and circuit breaker contacts to indicate an open circuit caused either by blowing of the fuse or tripping of the circuit breaker. A switch in the energizing circuit of the lamp prevents lighting thereof when the operating lever is in the OFF position. The interlock member carries current to the lamp and serves as a movable contact for the switch.