Add TODO option
diff --git a/TODO b/TODO
index 0e1e173..4b8db97 100644
--- a/TODO
+++ b/TODO
@@ -1,5 +1,7 @@
 - GNOME Bug 612402 - (hb-arm) HarfBuzz compilation fix for arm
 
+- Make sure LangSys default feature is only applied once...
+
 - kern/GPOS interaction
 
 - Use size_t in sanitize?