diff --git a/libretro.h b/libretro.h
index 1e715197bc..6100cc3a9c 100755
--- a/libretro.h
+++ b/libretro.h
@@ -750,10 +750,13 @@ struct retro_hw_render_callback
 // keycode is the RETROK value of the char.
 // character is the text character of the pressed key. (UTF-32).
 // key_modifiers is a set of RETROKMOD values or'ed together.
+//
 // The pressed/keycode state can be indepedent of the character.
 // It is also possible that multiple characters are generated from a single keypress.
-// The events should be treated separately, however, when possible, the frontend should
-// try to synchronize these.
+// Keycode events should be treated separately from character events.
+// However, when possible, the frontend should try to synchronize these.
+// If only a character is posted, keycode should be RETROK_UNKNOWN.
+// Similarily if only a keycode event is generated with no corresponding character, character should be 0.
 typedef void (*retro_keyboard_event_t)(bool down, unsigned keycode, uint32_t character, uint16_t key_modifiers);
 
 struct retro_keyboard_callback