diff --git a/Requirements.md b/Requirements.md
index 4981d9e..baa658a 100644
--- a/Requirements.md
+++ b/Requirements.md
@@ -8,6 +8,7 @@
   - [`mbstring`](https://secure.php.net/manual/en/book.mbstring.php) extension
   - [`simplexml`](https://secure.php.net/manual/en/book.simplexml.php) extension
   - [`curl`](https://secure.php.net/manual/en/book.curl.php) extension
+  - [`json`](https://secure.php.net/manual/en/book.json.php) extension
 
 Enable extensions by un-commenting the corresponding line in your PHP configuration (`php.ini`).