diff --git a/C64_joystick_atmelstudio/README.md b/C64_joystick_atmelstudio/README.md
index e9b956f..a4f92b9 100644
--- a/C64_joystick_atmelstudio/README.md
+++ b/C64_joystick_atmelstudio/README.md
@@ -5,7 +5,7 @@
 - LEFT(3) -> 14(PB3)
 - RIGHT(4) -> 15(PB1)
 - BTN1(6) -> 9(PB5)
-- BTN2(9, MSX 7) -> 8
+- BTN2(9, MSX 7) -> 8 (optional)
 - GND(8) -> GND(PB4)
 
 ## Firmware/flashing