A connector has a housing (11) with a cavity (12) for receiving a rectangular tube (Ta) of a terminal fitting (T). A lock (13) is formed on a surface of the cavity (12) for engaging the terminal fitting (T). The cavity (11) has a first guiding surface (14a) at a corner adjacent a surface of the cavity (12) opposed to the lock (13) for narrowing the width of a cavity (12). A retainer (21) engages a lower surface of the lock (13) for pressing the lock (13) and the terminal fitting (T) up into the first guiding surface (14a) to prevent shaking of the terminal fitting (T) in the cavity (12).