diff --git a/compiler/GHC/Cmm/Type.hs b/compiler/GHC/Cmm/Type.hs
index 8a750cd10d6d78d71c66b1c29c6ad91ae40d0d56..8cd502f8b7bff4b3e2828fdb3960956bc825dda9 100644
--- a/compiler/GHC/Cmm/Type.hs
+++ b/compiler/GHC/Cmm/Type.hs
@@ -311,6 +311,8 @@ isVecType _                       = False
 -- Hints are extra type information we attach to the arguments and
 -- results of a foreign call, where more type information is sometimes
 -- needed by the ABI to make the correct kind of call.
+--
+-- See Note [Signed vs unsigned] for one case where this is used.
 
 data ForeignHint
   = NoHint | AddrHint | SignedHint