A half-fitting prevention connector (200) includes a lock arm (53) which is formed on an outer surface of a housing (44) of a male connector (41), and substantially extends in a fitting direction of the male connector into a mating connector. The lock arm (53) locks the two connectors to each other in a fitted condition when a retaining projection (54), formed on the lock arm, is engaged in a retaining hole (58) formed in the female connector (42). A shutter (55) is formed at a distal end of the lock arm (53), and closes a terminal-fitting port (45a) in the male connector (41) when the retaining projection (54) is urged by a housing inner surface (64), and opens the terminal-fitting port (45a) when the retaining projection (54) is engaged in the retaining hole (58). A male terminal (62) is received in the female connector (42), and has a spring portion (62b) which can be compressively deformed along the terminal fitting direction.