A lock for an aircraft door. The lock includes an outer shell having an inner cavity. A core is rotatably mounted within the inner cavity to rotate about an axis of the core. The core has a keyhole extending through the core from a first end of the core for receiving a key therein, to an opposed second end of the core. The keyhole defines an air leakage path through the core. A cam has a cam arm mounted about the core and is rotatable therewith. The second end of the core protrudes from the cam. A cover is attached to the second end of the core. The cover blocks the keyhole at the second end of the core and obstructing the air leakage path. An aircraft door, methods, and a retrofit kit are also disclosed.