diff --git a/TODO b/TODO
index 7b446d7023b..e3a9f12bbc4 100644
--- a/TODO
+++ b/TODO
@@ -257,6 +257,7 @@ OSystem
   to common/system.cpp, or replace it with something better.
   No hasty changes here, please, make sure you understand how it is used right
   now before messing with it ;-)
+* Document key codes to be used for special keys, like F1-F15 etc.
 
 
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