An exterior operating handle is mounted on the wall of the enclosure of an enclosed-type circuit breaker and is drivingly connected to the operating handle of the circuit breaker. The cover is normally latched in closed position by a manually operable latch. Interlock means normally interlock the exterior handle, cover, and enclosure wall in a manner such that (a) when the cover is latched closed, the exterior handle can be operated to open and close the circuit breaker contacts, selectively; (b) when the cover is unlatched and the exterior handle in in ON position, the interlock means becomes operative to prevent opening of the cover; and (c) when the cover is unlatched or open and the exterior handle is in OFF position, the interlock becomes operative to prevent moving the exterior handle to ON position. If the contacts of the circuit breaker become welded together in closed position while the exterior handle is in ON position, and the exterior handle is moved manually to OFF position and the cover is then unlatched, the interlock means, which normally prevent moving the handle to ON position while the cover is unlatched, are defeated for an instant so as to permit the exterior handle to return automatically to ON position, thus preventing a false indication, and then become active again to interlock the cover and enclosure with the exterior handle in ON position.