diff --git a/package.json b/package.json
index 7f736eb1a..bd5189a0f 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "dist/vue-test-utils.cjs.js",
   "unpkg": "dist/vue-test-utils.browser.js",
   "types": "dist/index.d.ts",
-  "module": "dist/vue-test-utils.esm-bundler.js",
+  "module": "dist/vue-test-utils.esm-bundler.mjs",
   "files": [
     "dist",
     "README.md",
diff --git a/rollup.config.js b/rollup.config.js
index 81f7cc54d..9e031dd8c 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -55,7 +55,7 @@ function createEntry(options) {
   if (format === 'es') {
     config.output.file = pkg.module
     if (isBrowser) {
-      config.output.file = 'dist/vue-test-utils.esm-browser.js'
+      config.output.file = 'dist/vue-test-utils.esm-browser.mjs'
     }
   }
   if (format === 'cjs') {