diff --git a/plugins/helpers.nix b/plugins/helpers.nix
index c2a54dd5..eb505cb9 100644
--- a/plugins/helpers.nix
+++ b/plugins/helpers.nix
@@ -51,4 +51,11 @@ rec {
       key = key;
       mode = mode;
     }) normalized);
+
+  # Creates an option with a nullable type that defaults to null.
+  nullOrOption = type: desc: lib.mkOption {
+    type = lib.types.nullOr type;
+    default = null;
+    description = desc;
+  };
 }