diff --git a/src/mame/drivers/vegaeo.c b/src/mame/drivers/vegaeo.c
index 03d743eeeb6..b43fe4ab7c4 100644
--- a/src/mame/drivers/vegaeo.c
+++ b/src/mame/drivers/vegaeo.c
@@ -83,7 +83,7 @@ static READ32_HANDLER( vegaeo_custom_read )
 static ADDRESS_MAP_START( vega_map, ADDRESS_SPACE_PROGRAM, 32 )
 	AM_RANGE(0x00000000, 0x001fffff) AM_RAM
 	AM_RANGE(0x80000000, 0x80013fff) AM_READWRITE(vega_vram_r, vega_vram_w)
-	AM_RANGE(0xfc000000, 0xfc0000ff) AM_DEVREADWRITE8(AT28C16, "at28c16", at28c16_r, at28c16_w, 0xffffffff)
+	AM_RANGE(0xfc000000, 0xfc0000ff) AM_DEVREADWRITE8(AT28C16, "at28c16", at28c16_r, at28c16_w, 0x000000ff)
 	AM_RANGE(0xfc200000, 0xfc2003ff) AM_RAM_WRITE(vega_palette_w) AM_BASE(&paletteram32)
 	AM_RANGE(0xfc400000, 0xfc40005b) AM_WRITENOP // crt registers ?
 	AM_RANGE(0xfc600000, 0xfc600003) AM_WRITENOP // soundlatch