diff --git a/README.md b/README.md
index 6701ece..967a085 100644
--- a/README.md
+++ b/README.md
@@ -56,7 +56,7 @@
     $sitemap->write(__DIR__ . '/sitemap.txt', Sitemap::FORMAT_TXT);
     ```
 3. Sitemap index
-    ```
+    ```php
     $index = new Sitemapindex();
     $sitemap = new Sitemap($index);