A molded case circuit breaker includes a molded case containing a circuit breaker trip unit, and multiple line connector lugs attached to an end portion of the molded case for connecting the trip unit to power cables from a power source. Rigid support brackets attached to a rigid supporting surface extend along a pair of opposite outer side walls of the molded case adjacent the lugs to resist outward movement of the side walls in the event of a short circuit condition that exerts distorting forces on the lugs and the portions of the molded case adjacent the lugs. The rigid support brackets may be attached to a supporting pan attached to the portion of the molded case adjacent the lugs.