diff --git a/src/mame/drivers/mw18w.c b/src/mame/drivers/mw18w.c
index 901e457e543..1588c0fb656 100644
--- a/src/mame/drivers/mw18w.c
+++ b/src/mame/drivers/mw18w.c
@@ -63,11 +63,13 @@ ADDRESS_MAP_END
 static ADDRESS_MAP_START( mw18w_portmap, ADDRESS_SPACE_IO, 8 )
 	ADDRESS_MAP_UNMAP_HIGH
 	ADDRESS_MAP_GLOBAL_MASK(0xff)
+	AM_RANGE(0x00, 0x00) AM_MIRROR(4) AM_READ_PORT("IN0")
+	AM_RANGE(0x01, 0x01) AM_MIRROR(4) AM_READ_PORT("IN1")
+	AM_RANGE(0x02, 0x02) AM_MIRROR(4) AM_READ_PORT("IN2")
+	AM_RANGE(0x03, 0x03) AM_MIRROR(4) AM_READ_PORT("DSW")
 	AM_RANGE(0x00, 0x01) AM_WRITE(mw18w_sound_w)
-	AM_RANGE(0x01, 0x01) AM_READ_PORT("IN1")
-	AM_RANGE(0x02, 0x02) AM_READ_PORT("IN2") AM_WRITE(mw18w_lamps_w)
-	AM_RANGE(0x03, 0x03) AM_READ_PORT("DSW") AM_WRITE(mw18w_led_display_w)
-	AM_RANGE(0x04, 0x04) AM_READ_PORT("IN0")
+	AM_RANGE(0x02, 0x02) AM_WRITE(mw18w_lamps_w)
+	AM_RANGE(0x03, 0x03) AM_WRITE(mw18w_led_display_w)
 	AM_RANGE(0x06, 0x06) AM_WRITE(watchdog_reset_w)
 	AM_RANGE(0x07, 0x07) AM_WRITE(mw18w_irq0_clear_w)
 ADDRESS_MAP_END