diff --git a/package.json b/package.json
index fc8dfc7..4f911a8 100644
--- a/package.json
+++ b/package.json
@@ -3,6 +3,7 @@
   "version": "4.2.0",
   "description": "Fastify plugin to check environment variables",
   "main": "index.js",
+  "type": "commonjs",
   "types": "types/index.d.ts",
   "scripts": {
     "coverage": "cross-env VALUE_FROM_ENV=pippo tap --cov --coverage-report=html",