diff --git a/wp-admin/customize.php b/wp-admin/customize.php
index 0c9298784c..0dd548d43a 100644
--- a/wp-admin/customize.php
+++ b/wp-admin/customize.php
@@ -144,6 +144,10 @@ if ( is_rtl() ) {
 }
 $body_class .= ' locale-' . sanitize_html_class( strtolower( str_replace( '_', '-', get_user_locale() ) ) );
 
+if ( wp_use_widgets_block_editor() ) {
+	$body_class .= ' wp-embed-responsive';
+}
+
 $admin_title = sprintf( $wp_customize->get_document_title_template(), __( 'Loading…' ) );
 
 ?>
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b397efadf1..f0ed1970fc 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.8.1-alpha-51718';
+$wp_version = '5.8.1-alpha-51720';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.