diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,5 @@
+2022-01-03 v1.4.0.1
+	* Add haddock docs to makeDeltaAst
 2022-01-03 v1.4
 	* Fix handling of AnnContext (@pepeiborra)
 	* Fix crashy bogus instances (@pepeiborra)
diff --git a/ghc-exactprint.cabal b/ghc-exactprint.cabal
--- a/ghc-exactprint.cabal
+++ b/ghc-exactprint.cabal
@@ -1,5 +1,5 @@
 name:                ghc-exactprint
-version:             1.4.0
+version:             1.4.0.1
 synopsis:            ExactPrint for GHC
 description:         Using the API Annotations available from GHC 9.2.1, this
                      library provides a means to round trip any code that can
diff --git a/src/Language/Haskell/GHC/ExactPrint/ExactPrint.hs b/src/Language/Haskell/GHC/ExactPrint/ExactPrint.hs
--- a/src/Language/Haskell/GHC/ExactPrint/ExactPrint.hs
+++ b/src/Language/Haskell/GHC/ExactPrint/ExactPrint.hs
@@ -77,6 +77,9 @@
 exactPrintWithOptions r ast =
     runEP r (markAnnotated ast)
 
+-- | Transform concrete annotations into relative annotations which
+-- are more useful when transforming an AST. This corresponds to the
+-- earlier 'relativiseApiAnns'.
 makeDeltaAst :: ExactPrint ast => ast -> ast
 makeDeltaAst ast = fst $ runIdentity (runEP deltaOptions (markAnnotated ast))