A loading unit for a surgical stapling apparatus includes a shaft assembly, an end effector coupled to the shaft assembly, an I-beam assembly supported in the shaft assembly, and a fire lock assembly supported on the shaft assembly. The end effector is positioned to articulate relative to the shaft assembly between an unarticulated position and an articulated position. The I-beam assembly is selectively movable relative to the end effector to fire the end effector. The fire lock assembly is configured to prevent the I-beam assembly from firing the end effector when the end effector is disposed in the unarticulated position.
