diff --git a/package.json b/package.json
index a0ebf0c..cc30e39 100644
--- a/package.json
+++ b/package.json
@@ -6,7 +6,7 @@
   "type": "module",
   "scripts": {
     "dev": "tsx src/index.ts",
-    "build": "esbuild src/index.ts --bundle --platform=node --outfile=dist/oauth.cjs --minify && chmod +x dist/oauth.cjs",
+    "build": "esbuild src/index.ts --bundle --platform=node --outfile=dist/oauth.cjs '--external:*.pem' --minify && chmod +x dist/oauth.cjs",
     "prettify": "prettier --write ."
   },
   "dependencies": {
diff --git a/src/index.ts b/src/index.ts
index 7f5c4f6..1d5e3ce 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -9,11 +9,11 @@ import { readFile } from 'node:fs/promises'
 import { fileURLToPath } from 'node:url'
 
 const loadCerts = async (): Promise<SecureServerOptions> => {
-  const isCjs = !!global.require
+  const isCjs = !import.meta.resolve
   if (isCjs) {
     return {
-      cert: await readFile(global.require.resolve('./cert.pem')),
-      key: await readFile(global.require.resolve('./key.pem')),
+      cert: await readFile(require.resolve('./cert.pem')),
+      key: await readFile(require.resolve('./key.pem')),
     }
   } else {
     return {