diff --git a/src/mame/machine/snes.c b/src/mame/machine/snes.c
index d1173aaa4b9..310ddaf9d93 100644
--- a/src/mame/machine/snes.c
+++ b/src/mame/machine/snes.c
@@ -587,8 +587,8 @@ READ8_HANDLER( snes_r_io )
 
 	}
 
-	/* Unsupported reads return 0xff */
-	return 0xff;
+	/* Unsupported reads returns open bus */
+	return snes_open_bus_r(space,0);
 }
 
 /*