A female housing (40) has a lock arm (40) with an arm main body (43) that cantilevers back from the front of the female housing (40). A lock (46) is formed on the arm main body (43). An unlocking portion (44) is at the rear end of the arm main body (43) and extends normal to the arm main body (43). Arm portions (55) project obliquely downward from the opposite sides of the unlocking portion (44), and are coupled to protection walls (52) to sandwich the unlocking portion (44). Two restricting walls (55) project from the upper ends of the protection walls (52) at positions behind the arm portions (50) and higher than the arm portions (50) and face each other. The restricting walls (55) prevent an operator's finger from touching the arm portions (50).