diff --git a/packages/vite/src/node/config.ts b/packages/vite/src/node/config.ts
index 3ece9213dab76a..c81ab5807c5125 100644
--- a/packages/vite/src/node/config.ts
+++ b/packages/vite/src/node/config.ts
@@ -978,9 +978,11 @@ async function loadConfigFromBundledFile(
   fileName: string,
   bundledCode: string
 ): Promise<UserConfig> {
+  const extension = path.extname(fileName)
   const realFileName = fs.realpathSync(fileName)
-  const defaultLoader = _require.extensions['.js']
-  _require.extensions['.js'] = (module: NodeModule, filename: string) => {
+  const loaderExt = extension in _require.extensions ? extension : '.js'
+  const defaultLoader = _require.extensions[loaderExt]!
+  _require.extensions[loaderExt] = (module: NodeModule, filename: string) => {
     if (filename === realFileName) {
       ;(module as NodeModuleWithCompile)._compile(bundledCode, filename)
     } else {
@@ -990,7 +992,7 @@ async function loadConfigFromBundledFile(
   // clear cache in case of server restart
   delete _require.cache[_require.resolve(fileName)]
   const raw = _require(fileName)
-  _require.extensions['.js'] = defaultLoader
+  _require.extensions[loaderExt] = defaultLoader
   return raw.__esModule ? raw.default : raw
 }