An anvil assembly includes a retaining member having a body portion and a frangible portion connected to the body portion, where the frangible portion is positioned to engage a backup member and separates from the body portion during movement of the backup member from a first, proximal position to a second, distal position. The retaining member keeps the backup plate in the proximal position prior to firing of the stapling assembly, and upon separation of the frangible portion allows the backup plate to move to the distal position during firing of the stapling assembly. Proximal force on the backup plate after firing of the stapling assembly is avoided, thereby helping to ensure titling of the anvil assembly.
