diff --git a/Cabal/Distribution/Utils/StructuredBinary.hs b/Cabal/Distribution/Utils/StructuredBinary.hs
index e776fb9c4a1885a5a8ed8bf204e0ae7d6c374a6e..37fc48b3a0dbf43b938a515329edb9eeb74ceeec 100644
--- a/Cabal/Distribution/Utils/StructuredBinary.hs
+++ b/Cabal/Distribution/Utils/StructuredBinary.hs
@@ -202,7 +202,7 @@ structureHash _ = untag (structureHash' :: Tagged a MD5)
 
 -- | Structured 'Binary.encode'.
 -- Encode a value to using binary serialisation to a lazy 'LBS.ByteString'.
--- Encoding starts with 20 byte large structure hash.
+-- Encoding starts with 16 byte large structure hash.
 structuredEncode
   :: forall a. (Binary.Binary a, Structured a)
   => a -> LBS.ByteString