diff --git a/flake.nix b/flake.nix
index 5dc53bb..3e641b8 100644
--- a/flake.nix
+++ b/flake.nix
@@ -38,5 +38,7 @@
     mergeListsToAttrs = names: values: nixpkgs.lib.listToAttrs (nixpkgs.lib.zipListsWith (name: value: { inherit name value; }) names values);
 
     mkEnumFromDirContents = dir: nixpkgs.lib.types.enum (map (name: nixpkgs.lib.removeSuffix ".nix" name) (builtins.attrNames (builtins.readDir dir)));
+
+    mkOptionalListOfType = type: nixpkgs.lib.types.either (type) (nixpkgs.lib.types.listOf (type));
   };
 }