diff --git a/pkgs/development/haskell-modules/lib.nix b/pkgs/development/haskell-modules/lib.nix
index b730ef9b2ed..c9dc7254800 100644
--- a/pkgs/development/haskell-modules/lib.nix
+++ b/pkgs/development/haskell-modules/lib.nix
@@ -385,7 +385,7 @@ rec {
   # Utility to convert a directory full of `cabal2nix`-generated files into a
   # package override set
   #
-  # packagesFromDirectory : Directory -> HaskellPackageOverrideSet
+  # packagesFromDirectory : { directory : Directory, ... } -> HaskellPackageOverrideSet
   packagesFromDirectory =
     { directory, ... }: