An assembly including a nacelle element, such as a cover, a device for locking the nacelle element, a key for locking/unlocking the locking device and an indicator for indicating the position of the locking device. This assembly includes a control device which is configured to be actuated by the key when the key is withdrawn from the locking device so as to make the indicator move from a first state to a second state, the state of the indicator being representative of the locked or unlocked position of the locking device.