A surgical stapling instrument (10) includes an anvil body (12) defining a longitudinal axis, a cartridge body (14) coupled to the anvil body (12), a staple cartridge (18) releasably mounted relative to the cartridge body (14), a firing member (34) mounted to the cartridge body (14) and configured for longitudinal movement through the staple cartridge (18), and a lockout member (36) supported by the cartridge body (14). The lockout member (36) defines a single longitudinal slot (40) for at least partial reception of the firing member (34). The lockout member (36) is configured for movement from a locked position preventing longitudinal movement of the firing member (34) to a release position permitting longitudinal movement of the firing member (34) upon mounting of the staple cartridge (18) to the cartridge body (14).
