diff --git a/post-content.php b/post-content.php
index 56a0f386f0a0e0..8d6ea418977bc0 100644
--- a/post-content.php
+++ b/post-content.php
@@ -131,8 +131,8 @@
 <p><?php _e( 'Any block can opt into these alignments. The embed block has them also, and is responsive out of the box:', 'gutenberg' ); ?></p>
 <!-- /wp:paragraph -->
 
-<!-- wp:core-embed/vimeo {"url":"https://vimeo.com/22439234","align":"wide","type":"video","providerNameSlug":"vimeo"} -->
-<figure class="wp-block-embed-vimeo alignwide wp-block-embed is-type-video is-provider-vimeo"><div class="wp-block-embed__wrapper">
+<!-- wp:core-embed/vimeo {"url":"https://vimeo.com/22439234","type":"video","providerNameSlug":"vimeo","align":"wide","className":"wp-has-aspect-ratio wp-embed-aspect-16-9"} -->
+<figure class="wp-block-embed-vimeo alignwide wp-block-embed is-type-video is-provider-vimeo wp-has-aspect-ratio wp-embed-aspect-16-9"><div class="wp-block-embed__wrapper">
 https://vimeo.com/22439234
 </div></figure>
 <!-- /wp:core-embed/vimeo -->