diff --git a/src/mame/drivers/warriorb.cpp b/src/mame/drivers/warriorb.cpp
index d8192a8eff0..38596e98d4f 100644
--- a/src/mame/drivers/warriorb.cpp
+++ b/src/mame/drivers/warriorb.cpp
@@ -249,7 +249,7 @@ ADDRESS_MAP_START(warriorb_state::warriorb_map)
 	AM_RANGE(0x400000, 0x400007) AM_DEVREADWRITE("tc0110pcr_1", tc0110pcr_device, word_r, step1_word_w)    /* palette (1st screen) */
 	AM_RANGE(0x420000, 0x420007) AM_DEVREADWRITE("tc0110pcr_2", tc0110pcr_device, word_r, step1_word_w)    /* palette (2nd screen) */
 	AM_RANGE(0x600000, 0x6013ff) AM_RAM AM_SHARE("spriteram")
-	AM_RANGE(0x800000, 0x80000f) AM_DEVREADWRITE("tc0510nio", tc0510nio_device, halfword_r, halfword_w)
+	AM_RANGE(0x800000, 0x80000f) AM_DEVREADWRITE8("tc0510nio", tc0510nio_device, read, write, 0x00ff)
 //  AM_RANGE(0x820000, 0x820001) AM_WRITENOP    // ? uses bits 0,2,3
 	AM_RANGE(0x830000, 0x830003) AM_READWRITE(sound_r, sound_w)
 ADDRESS_MAP_END