The present disclosure provides a surgical instrument, such as a tissue sealing instrument, with an elongate shaft and first and second jaws movably coupled to the shaft. The second jaw comprises a cavity for receiving a staple cartridge and a substantially longitudinal reinforcing wall extending through the cavity. The instrument further includes a drive member configured to translate through the end effector to close the jaws and to engage a plurality of staples within the staple cartridge to drive the staples into tissue. The reinforcing wall provides additional support for the staple cartridge to inhibit deformation of the staple cartridge during actuation, thereby improving the staple formation in the tissue. This improves the tissue seal provided by the staples without increasing the overall size of the end effector.