diff --git a/package.json b/package.json
index 45e1c27..8de7094 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,7 @@
     "url": "git+https://github.com/fastify/fastify-auth.git"
   },
   "main": "auth.js",
+  "type": "commonjs",
   "types": "types/index.d.ts",
   "scripts": {
     "clean": "rimraf authdb",