diff --git a/src/Hpack/Yaml.hs b/src/Hpack/Yaml.hs
index fbe39dd3..18b366ce 100644
--- a/src/Hpack/Yaml.hs
+++ b/src/Hpack/Yaml.hs
@@ -14,6 +14,7 @@ module Hpack.Yaml (
 -- tool that supports Hpack (e.g. @stack@ or @cabal2nix@).
 
   decodeYaml
+, formatWarning
 , module Data.Aeson.Config.FromValue
 ) where