diff --git a/src/user_config.h b/src/user_config.h
index 194ad9c..36e3872 100644
--- a/src/user_config.h
+++ b/src/user_config.h
@@ -23,6 +23,12 @@
  *
  * defined as HID_KEY_<something>
  *
+ * If you do not want to use a key for switching outputs, you may be tempted
+ * to select HID_KEY_NONE here; don't do that! That code appears in many HID
+ * messages and the result will be a non-functional keyboard. Instead, choose
+ * a key that is unlikely to ever appear on a keyboard that you will use.
+ * HID_KEY_F24 is probably a good choice as keyboards with 24 function keys
+ * are rare.
  * */
 
 #define HOTKEY_TOGGLE HID_KEY_CAPS_LOCK
@@ -70,4 +76,4 @@
  * */
 
 #define SCREENSAVER_ENABLED  0
-#define SCREENSAVER_TIME_SEC 240
\ No newline at end of file
+#define SCREENSAVER_TIME_SEC 240