diff --git a/src/mame/drivers/s11a.c b/src/mame/drivers/s11a.c
index eb3dfe69be0..3c39bfb34fa 100644
--- a/src/mame/drivers/s11a.c
+++ b/src/mame/drivers/s11a.c
@@ -139,6 +139,7 @@ static ADDRESS_MAP_START( s11a_bg_map, AS_PROGRAM, 8, s11a_state )
 	AM_RANGE(0x0000, 0x07ff) AM_MIRROR(0x1800) AM_RAM
 	AM_RANGE(0x2000, 0x2001) AM_MIRROR(0x1ffe) AM_DEVREADWRITE("ym2151", ym2151_device, read, write)
 	AM_RANGE(0x4000, 0x4003) AM_MIRROR(0x1ffc) AM_DEVREADWRITE("pia40", pia6821_device, read, write)
+	AM_RANGE(0x7800, 0x7fff) AM_WRITE(bgbank_w)
 	AM_RANGE(0x8000, 0xffff) AM_ROMBANK("bgbank")
 ADDRESS_MAP_END