diff --git a/src/wp-admin/customize.php b/src/wp-admin/customize.php
index 0c9298784c..0dd548d43a 100644
--- a/src/wp-admin/customize.php
+++ b/src/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…' ) );
 
 ?>