diff --git a/index.js b/index.mjs
similarity index 100%
rename from index.js
rename to index.mjs
diff --git a/jest.config.cjs b/jest.config.cjs
new file mode 100644
index 0000000..7f8b211
--- /dev/null
+++ b/jest.config.cjs
@@ -0,0 +1,6 @@
+module.exports = {
+  transform: {
+    "^.+\\.mjs$": "babel-jest",
+    "^.+\\.ts$": "babel-jest",
+  },
+}
\ No newline at end of file
diff --git a/package.json b/package.json
index 813df85..018806a 100644
--- a/package.json
+++ b/package.json
@@ -3,7 +3,7 @@
   "version": "2.0.0",
   "description": "How to easy collect unsubscribe functions from several sources",
   "type": "module",
-  "main": "index.js",
+  "main": "index.mjs",
   "types": "index.d.ts",
   "scripts": {
     "test": "jest"