diff --git a/package.json b/package.json
index d3550a3..9c73895 100644
--- a/package.json
+++ b/package.json
@@ -1,10 +1,13 @@
 {
+    "type": "module",
     "dependencies": {
+        "@yanick/updeep": "../updeep",
         "lodash": "^4.17.15",
+        "lodash-es": "^4.17.21",
         "redux": "^4.0.5",
         "ts-action": "^11.0.0",
         "ts-node": "^8.6.2",
-        "@yanick/updeep": "^2.2.0"
+        "updeep": "^1.2.1"
     },
     "devDependencies": {
         "@babel/cli": "^7.8.4",
@@ -16,6 +19,7 @@
         "@typescript-eslint/eslint-plugin": "^2.23.0",
         "@typescript-eslint/parser": "^2.23.0",
         "babel-jest": "^25.1.0",
+        "chai": "^4.3.4",
         "docsify": "^4.11.2",
         "docsify-cli": "^4.4.0",
         "docsify-tools": "^1.0.20",
@@ -29,12 +33,13 @@
         "promake": "^3.1.3",
         "sinon": "^9.0.1",
         "standard-version": "^8.0.0",
-        "tap": "^14.10.6",
+        "tap": "15",
         "ts-jest": "^25.2.1",
         "tsd": "^0.11.0",
         "typedoc": "0.17.7",
         "typedoc-plugin-markdown": "^2.2.17",
-        "typescript": "^4.2.0"
+        "typescript": "^4.2.0",
+        "uvu": "^0.5.1"
     },
     "license": "MIT",
     "main": "dist/index.js",
diff --git a/src/buildInitial/index.js b/src/buildInitial/index.js
new file mode 100644
index 0000000..b387363
--- /dev/null
+++ b/src/buildInitial/index.js
@@ -0,0 +1,15 @@
+import { isPlainObject, mapValues } from 'lodash-es';
+import u from '@yanick/updeep';
+
+export function buildInitial(initial, subduxes = {}) {
+    if (!isPlainObject(initial) && Object.keys(subduxes).length > 0)
+        throw new Error(
+            "can't have subduxes on a dux which state is not an object"
+        );
+
+    const subInitial = mapValues(subduxes, ({ initial }, key) =>
+        key === '*' ? [] : initial
+    );
+
+    return u(initial, subInitial);
+}
diff --git a/src/buildInitial/index.ts b/src/buildInitial/index.ts
deleted file mode 100644
index 3ecf225..0000000
--- a/src/buildInitial/index.ts
+++ /dev/null
@@ -1,16 +0,0 @@
-import fp from 'lodash/fp';
-import u from '@yanick/updeep';
-
-function buildInitial(initial: any, coduxes: any = [], subduxes: any = {}) {
-    if (!fp.isPlainObject(initial)) return initial;
-
-    return fp.flow(
-        [
-            u(fp.omit(['*'], subduxes)),
-            coduxes.map(i => u(i)),
-            u(initial),
-        ].flat()
-    )({});
-}
-
-export default buildInitial;
diff --git a/src/buildInitial/test.js b/src/buildInitial/test.js
new file mode 100644
index 0000000..5977827
--- /dev/null
+++ b/src/buildInitial/test.js
@@ -0,0 +1,12 @@
+import { test } from 'tap';
+
+import { buildInitial } from './index.js';
+
+test('basic', async (t) => {
+    t.same(
+        buildInitial({ a: 1 }, { b: { initial: { c: 2 } } })
+    ,{
+        a: 1,
+        b: { c: 3 },
+    });
+});