diff --git a/src/mame/sega/naomigd.cpp b/src/mame/sega/naomigd.cpp
index b67ae0c1183..57dbf3ecd0c 100644
--- a/src/mame/sega/naomigd.cpp
+++ b/src/mame/sega/naomigd.cpp
@@ -1141,11 +1141,11 @@ ROM_START( dimm )
 	ROMX_LOAD( "217_203.bin",     0x000000, 0x200000, CRC(a738ea1c) SHA1(e5a229ae7ed48b2955cad63529fd938c6db555e5), ROM_BIOS(4))
 	ROM_SYSTEM_BIOS(5, "3.01", "BIOS 5")
 	ROMX_LOAD( "fpr23905c.ic36",  0x000000, 0x200000, CRC(ffffffff) SHA1(972b3b73aa1eabb1091e9096b57a7e5e1d0436d8), ROM_BIOS(5))
-	ROM_SYSTEM_BIOS(5, "3.03", "BIOS 6")
+	ROM_SYSTEM_BIOS(6, "3.03", "BIOS 6")
 	ROMX_LOAD( "fpr23905.ic36",   0x000000, 0x200000, CRC(ffffffff) SHA1(acade4362807c7571b1c2a48ed6067e4bddd404b), ROM_BIOS(6))
-	ROM_SYSTEM_BIOS(6, "317_312.bin", "BIOS 7")
+	ROM_SYSTEM_BIOS(7, "317_312.bin", "BIOS 7")
 	ROMX_LOAD( "317_312.bin",     0x000000, 0x200000, CRC(a738ea1c) SHA1(31d698cd659446ee09a2eeedec6e4bc6a19d05e8), ROM_BIOS(7))
-	ROM_SYSTEM_BIOS(7, "401_203.bin", "BIOS 8")
+	ROM_SYSTEM_BIOS(8, "401_203.bin", "BIOS 8")
 	ROMX_LOAD( "401_203.bin",     0x000000, 0x200000, CRC(a738ea1c) SHA1(edb52597108462bcea8eb2a47c19e51e5fb60638), ROM_BIOS(8))
 
 	// dynamically filled with data