diff --git a/nixos/modules/services/games/factorio.nix b/nixos/modules/services/games/factorio.nix
index 0dcd5b1cebdb..1b2f5bd840b5 100644
--- a/nixos/modules/services/games/factorio.nix
+++ b/nixos/modules/services/games/factorio.nix
@@ -140,7 +140,9 @@ in
         type = types.nullOr types.path;
         default = null;
         description = lib.mdDoc ''
-        Mods settings can be changed by specifying a dat file.
+          Mods settings can be changed by specifying a dat file, in the [mod
+          settings file
+          format](https://wiki.factorio.com/Mod_settings_file_format).
         '';
       };
       game-name = mkOption {
diff --git a/pkgs/games/factorio/utils.nix b/pkgs/games/factorio/utils.nix
index 86b0b2f85104..d2b52ae48366 100644
--- a/pkgs/games/factorio/utils.nix
+++ b/pkgs/games/factorio/utils.nix
@@ -18,9 +18,9 @@ with lib;
           # NB: there will only ever be a single zip file in each mod derivation's output dir
           ln -s $modDrv/*.zip $out
         done
-      '' + (if modsDatFile != null then ''
+      '' + (lib.optionalString (modsDatFile != null) ''
        cp ${modsDatFile} $out/mod-settings.dat
-      '' else "");
+      '');
     };
 
     modDrv = { allRecommendedMods, allOptionalMods }: