Abstract: A connector assembly including a first connector having female terminals which are short-circuited through a short-circuiting terminal while the first connector is not connected to a second one. When the second connector is plugged into the first connector, an insulating piece of the second connector breaks the short-circuit connection between the female terminals. The short-circuiting terminal has contact portions. At least one of the short-circuiting terminal contact portions has a side extension. The second connector has a rib adapted to press the contact portions to form a gap between the short-circuiting terminals and the female terminals. The insulating piece is inserted between the gap thus formed, so that it encounters practically no resistance. Accordingly, it is possible to reduce the thickness of the insulating piece and thus to improve the long-term reliability of the connector assembly.