diff --git a/src/mame/drivers/electron.cpp b/src/mame/drivers/electron.cpp
index 81f7123b72a..8d289364d29 100644
--- a/src/mame/drivers/electron.cpp
+++ b/src/mame/drivers/electron.cpp
@@ -203,7 +203,7 @@ static INPUT_PORTS_START( electron64 )
 	PORT_CONFNAME(0x03, 0x01, "MRB Mode")
 	PORT_CONFSETTING(0x00, "Normal")
 	PORT_CONFSETTING(0x01, "Turbo")
-	PORT_CONFSETTING(0x02, "Shadow")
+	PORT_CONFSETTING(0x02, "64K")
 INPUT_PORTS_END
 
 MACHINE_CONFIG_START(electron_state::electron)
@@ -270,7 +270,7 @@ ROM_END
 
 ROM_START(electron64)
 	ROM_REGION( 0x4000, "mos", 0 )
-	ROM_LOAD( "os_mrb.rom", 0x0000, 0x4000, CRC(0886741b) SHA1(2863b45dc880a7ed91ad9828795a3eb5ed0bcdd4) )
+	ROM_LOAD( "os_300.rom", 0x0000, 0x4000, CRC(f80a0cea) SHA1(165e42ff4164a842e56f08ebd420d5027af99fdd) )
 	ROM_REGION(0x4000, "basic", 0)
 	ROM_LOAD( "basic.rom", 0x0000, 0x4000, CRC(79434781) SHA1(4a7393f3a45ea309f744441c16723e2ef447a281) )
 ROM_END