diff --git a/packages/next-mdx/readme.md b/packages/next-mdx/readme.md
index 250906682e3b..2b7941901d2c 100644
--- a/packages/next-mdx/readme.md
+++ b/packages/next-mdx/readme.md
@@ -51,7 +51,8 @@ module.exports = withMDX({
 })
 ```
 
-Optionally you can match other file extensions for MDX compilation, by default only `.mdx` is supported
+By default MDX will only match and compile MDX files with the `.mdx` extension.
+However, it can also be optionally configured to handle markdown files with the `.md` extension, as shown below:
 
 ```js
 // next.config.js
@@ -61,6 +62,8 @@ const withMDX = require('@next/mdx')({
 module.exports = withMDX()
 ```
 
+In addition, MDX can be customized with compiler options, see the [mdx documentation](https://mdxjs.com/packages/mdx/#compilefile-options) for details on supported options.
+
 ## Top level .mdx pages
 
 Define the `pageExtensions` option to have Next.js handle `.md` and `.mdx` files in the `pages` directory as pages: