diff --git a/projects/default.nix b/projects/default.nix
index ef59c71f8..435e1bd6d 100644
--- a/projects/default.nix
+++ b/projects/default.nix
@@ -36,11 +36,17 @@ let
         else
           assert elem name allowedFiles;
           { };
-      allowedFiles = [
-        "README.md"
-        "default.nix"
-        "models.nix"
-      ];
+      allowedFiles =
+        [
+          "README.md"
+          "default.nix"
+          "models.nix"
+        ]
+        # TODO: remove after fully migrating types to the module system
+        ++ [
+          "default-module.nix"
+          "types.nix"
+        ];
     in
     # TODO: use fileset and filter for `gitTracked` files
     concatMapAttrs names (readDir baseDirectory);
diff --git a/projects/types.nix b/projects/types.nix
new file mode 100644
index 000000000..a114fedc5
--- /dev/null
+++ b/projects/types.nix
@@ -0,0 +1,23 @@
+{
+  lib,
+  ...
+}:
+let
+  inherit (lib)
+    types
+    mkOption
+    ;
+in
+{
+  subgrant =
+    with types;
+    submodule {
+      options = lib.genAttrs [ "Commons" "Core" "Entrust" "Review" ] (
+        name:
+        mkOption {
+          type = listOf str;
+          default = [ ];
+        }
+      );
+    };
+}