A door of a vehicle having a door inner panel, a door latch assembly mounted to the inner panel adjacent to a fish mouth opening, with the latch assembly having a lock lever; and a door trim panel mounted on the inner panel including a lock hole on a surface of the trim panel. A manual lock assembly has a mounting bracket, a button cap, a main shaft and a cam. The mounting bracket is mounted to the door trim panel. The button cap telescopically slides in the bracket and has an end extending through the lock hole. The main shaft slides in the bracket, engages with the button cap and extends into contact with the cam. The cam engages the lock lever to cause locking of the latch assembly when the button cap is pushed.