diff --git a/Dockerfile b/Dockerfile
index 4041ed5..9d435de 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,7 +1,7 @@
 FROM node:18-alpine
 
-COPY dist/index.js /index.js
+COPY dist/index.mjs /index.mjs
 
 RUN apk add --no-cache git
 
-ENTRYPOINT [ "node", "/index.js" ]
+ENTRYPOINT [ "node", "/index.mjs" ]
diff --git a/dist/index.js b/dist/index.mjs
similarity index 100%
rename from dist/index.js
rename to dist/index.mjs
diff --git a/esbuild.config.js b/esbuild.config.js
index a71d6fc..5649409 100644
--- a/esbuild.config.js
+++ b/esbuild.config.js
@@ -21,6 +21,7 @@ const options = {
     format: 'esm',
     outdir: 'dist',
     outbase: 'src',
+    outExtension: { '.js': '.mjs' },
 };
 
 esbuild.build(options).catch(err => {
diff --git a/package.json b/package.json
index d9a8ae5..e8490b1 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
     "name": "eslint-remote-tester-run-action",
     "version": "0.0.1",
     "description": "GitHub Action for running eslint-remote-tester",
-    "main": "dist/index.js",
+    "main": "dist/index.mjs",
     "type": "module",
     "repository": "https://github.com/AriPerkkio/eslint-remote-tester-run-action",
     "homepage": "https://github.com/AriPerkkio/eslint-remote-tester-run-action",