diff --git a/ReadMe.md b/ReadMe.md
index b6f9b10..c3ef7f3 100644
--- a/ReadMe.md
+++ b/ReadMe.md
@@ -7,7 +7,7 @@ Unofficial [MDX][1] 3 [transformer plugin][2] for [Parcel][3] 2
 
 [![NPM](https://nodei.co/npm/parcel-transformer-mdx.png?downloads=true&downloadRank=true&stars=true)][6]
 
-## Supported features
+## Preset features
 
 1. [GitHub flavored Markdown (GFM)](https://github.com/remarkjs/remark-gfm)
 2. [Frontmatter](https://github.com/remarkjs/remark-frontmatter)
@@ -95,6 +95,10 @@ https://www.youtube.com/watch?v=VEoMT8pAxMA
 
 -   WebCell example: https://github.com/EasyWebApp/BootCell-document
 
+## Custom Configuration
+
+Create a `mdx.config.js` file in the root folder of your project, and export your [`CompileOptions` object][7] as what [the internal preset][8] does.
+
 ## Inspiration
 
 https://github.com/parcel-bundler/parcel/pull/7922
@@ -105,3 +109,5 @@ https://github.com/parcel-bundler/parcel/pull/7922
 [4]: https://libraries.io/npm/parcel-transformer-mdx
 [5]: https://github.com/EasyWebApp/Parcel-transformer-MDX/actions/workflows/main.yml
 [6]: https://nodei.co/npm/parcel-transformer-mdx/
+[7]: https://mdxjs.com/packages/mdx/#compileoptions
+[8]: source/preset.js
diff --git a/index.js b/index.js
index 34378ab..78748e6 100644
--- a/index.js
+++ b/index.js
@@ -1,22 +1,18 @@
 import { Transformer } from '@parcel/plugin';
 import { compile } from '@mdx-js/mdx';
 
-import MDXPreset from './source/preset';
-import { BabelConfigFiles, MDXConfigFiles } from './source/utility';
+import MDXPreset from './source/preset.js';
+import { BabelConfigFiles, MDXConfigFiles } from './source/utility.js';
 
 export { MDXPreset };
-export * from './source/utility';
+export * from './source/utility.js';
 
 export default new Transformer({
     /**
      * @returns {Promise<import('@mdx-js/mdx').CompileOptions>}
      */
     async loadConfig({ config }) {
-        const [
-            { contents: TSConfig },
-            { contents: BabelConfig },
-            { contents: MDXConfig }
-        ] = await Promise.all([
+        const [TSConfig, BabelConfig, MDXConfig] = await Promise.all([
             config.getConfig(['tsconfig.json', 'jsconfig.json']),
             config.getConfig(BabelConfigFiles, { packageKey: 'babel' }),
             config.getConfig(MDXConfigFiles, { packageKey: 'mdx' })
@@ -25,12 +21,12 @@ export default new Transformer({
          * @type {import('types-tsconfig').TSConfigJSON['compilerOptions']}
          */
         const { jsx, jsxImportSource, jsxFactory, jsxFragmentFactory } =
-            TSConfig?.compilerOptions || {};
+            TSConfig?.contents.compilerOptions || {};
         /**
          * @see {@link https://babeljs.io/docs/babel-preset-react#with-a-configuration-file-recommended}
          */
         const [_, ReactPreset = {}] =
-            BabelConfig?.presets?.find(
+            BabelConfig?.contents.presets?.find(
                 preset =>
                     preset instanceof Array &&
                     preset[0] === '@babel/preset-react'
@@ -46,7 +42,7 @@ export default new Transformer({
             pragma: pragma || jsxFactory,
             pragmaFrag: pragmaFrag || jsxFragmentFactory,
             ...MDXPreset,
-            ...MDXConfig
+            ...MDXConfig?.contents
         };
     },
     async transform({ asset, config }) {
diff --git a/package.json b/package.json
index 616bb30..63b935b 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name": "parcel-transformer-mdx",
-    "version": "0.4.0",
+    "version": "0.4.2",
     "license": "LGPL-3.0-or-later",
     "author": "shiy2008@gmail.com",
     "description": "Unofficial MDX 3 transformer plugin for Parcel 2",