diff --git a/overlays/30-ghc.nix b/overlays/30-ghc.nix
index 2c46abcb..d46d1cfa 100644
--- a/overlays/30-ghc.nix
+++ b/overlays/30-ghc.nix
@@ -14,6 +14,7 @@ let
       inherit (p)
         brittany ormolu releaser cabal-fmt stack ghcid ghcide arbtt iCalendar
         pretty-simple tz
+        # stm-containers
         haskell-language-server cabal-install dhall taskwarrior pandoc hlint
         cabal2nix weeder reflex-dom password optics shh-extras neuron
         hspec-discover paths hmatrix postgresql-simple snap