diff --git a/src/mame/drivers/plus4.cpp b/src/mame/drivers/plus4.cpp
index 17c8906b5a1..8bf79acbfc5 100644
--- a/src/mame/drivers/plus4.cpp
+++ b/src/mame/drivers/plus4.cpp
@@ -1183,11 +1183,11 @@ ROM_START( plus4p )
 
 	ROM_DEFAULT_BIOS("r5")
 	ROM_SYSTEM_BIOS( 0, "r3", "Revision 3" )
-	ROMX_LOAD( "318004-03.u4", 0x4000, 0x4000, CRC(77bab934) SHA1(97814dab9d757fe5a3a61d357a9a81da588a9783), ROM_BIOS(1) )
+	ROMX_LOAD( "318004-03.u24", 0x4000, 0x4000, CRC(77bab934) SHA1(97814dab9d757fe5a3a61d357a9a81da588a9783), ROM_BIOS(1) )
 	ROM_SYSTEM_BIOS( 1, "r4", "Revision 4" )
-	ROMX_LOAD( "318004-04.u4", 0x4000, 0x4000, CRC(be54ed79) SHA1(514ad3c29d01a2c0a3b143d9c1d4143b1912b793), ROM_BIOS(2) )
+	ROMX_LOAD( "318004-04.u24", 0x4000, 0x4000, CRC(be54ed79) SHA1(514ad3c29d01a2c0a3b143d9c1d4143b1912b793), ROM_BIOS(2) )
 	ROM_SYSTEM_BIOS( 2, "r5", "Revision 5" )
-	ROMX_LOAD( "318004-05.u4", 0x4000, 0x4000, CRC(71c07bd4) SHA1(7c7e07f016391174a557e790c4ef1cbe33512cdb), ROM_BIOS(3) )
+	ROMX_LOAD( "318004-05.u24", 0x4000, 0x4000, CRC(71c07bd4) SHA1(7c7e07f016391174a557e790c4ef1cbe33512cdb), ROM_BIOS(3) )
 
 	ROM_REGION( 0x8000, "function", 0 )
 	ROM_LOAD( "317053-01.u25", 0x0000, 0x4000, CRC(4fd1d8cb) SHA1(3b69f6e7cb4c18bb08e203fb18b7dabfa853390f) )