A slam-shut safety device includes a valve body defining a flow path, a valve disc support, and a valve disc that is mounted on the valve disc support and is movable between an open first position spaced away from the valve seat and a closed second position seated against a valve seat. A reset pin is operatively coupled to the valve disc support and is shiftable between an untripped position placing the valve disc in the open position and a tripped position placing the valve disc in the closed position. An anti-rotation assembly is carried by cooperating portions of the valve disc and the valve disc support, with the anti-rotation assembly comprising at least one protrusion and at least one receiving area sized to receive the protrusion, the anti-rotation assembly arranged to stop rotation of the valve disc relative to the valve disc support.