diff --git a/src/mame/drivers/dec0.cpp b/src/mame/drivers/dec0.cpp
index 9518cd340a7..3f87b4b2ba4 100644
--- a/src/mame/drivers/dec0.cpp
+++ b/src/mame/drivers/dec0.cpp
@@ -646,8 +646,11 @@ static ADDRESS_MAP_START( midres_map, AS_PROGRAM, 16, dec0_state )
 ADDRESS_MAP_END
 
 static ADDRESS_MAP_START( midresb_map, AS_PROGRAM, 16, dec0_state )
+	AM_RANGE(0x160010, 0x160011) AM_WRITE(dec0_priority_w)
 	AM_RANGE(0x180000, 0x18000f) AM_READ(dec0_controls_r)
+	AM_RANGE(0x180012, 0x180013) AM_NOP
 	AM_RANGE(0x180014, 0x180015) AM_WRITE(midres_sound_w)
+	AM_RANGE(0x180018, 0x180019) AM_NOP
 	AM_RANGE(0x1a0000, 0x1a0001) AM_READ_PORT("AN0")
 	AM_RANGE(0x1a0008, 0x1a0009) AM_READ_PORT("AN1")
 	AM_IMPORT_FROM( midres_map )