diff --git a/src/mame/drivers/coco12.cpp b/src/mame/drivers/coco12.cpp
index becc3b84772..1f943703c6a 100644
--- a/src/mame/drivers/coco12.cpp
+++ b/src/mame/drivers/coco12.cpp
@@ -610,13 +610,13 @@ ROM_END
 
 ROM_START(cd6809)
 	ROM_REGION(0x8000,MAINCPU_TAG,0)
-        ROM_DEFAULT_BIOS("1984")
+        ROM_DEFAULT_BIOS("84")
 
         ROM_SYSTEM_BIOS( 0, "83", "1983" )
 	ROMX_LOAD("cd6809bas83.rom",    0x2000, 0x2000, CRC(f8e64142) SHA1(c0fd689119e2619ec226a2d67aeeb32070c14e38), ROM_BIOS(1))
 	ROMX_LOAD("cd6809extbas83.rom", 0x0000, 0x2000, CRC(e5d5aa15) SHA1(0cd4a3d9e4af1d0176964e35e3d15a9fa0e68ac4), ROM_BIOS(1))
 
-        ROM_SYSTEM_BIOS( 0, "84", "1984" )
+        ROM_SYSTEM_BIOS( 1, "84", "1984" )
 	ROMX_LOAD("cd6809bas84.rom",    0x2000, 0x2000, CRC(8a9971da) SHA1(5cb5f1ffc983a85ba92af68b1d571b270f6db559), ROM_BIOS(2))
 	ROMX_LOAD("cd6809extbas84.rom", 0x0000, 0x2000, CRC(8dc853e2) SHA1(d572ce4497c115af53d2b0feeb52d3c7a7fec175), ROM_BIOS(2))
 ROM_END