diff --git a/wp-includes/rest-api/endpoints/class-wp-rest-sidebars-controller.php b/wp-includes/rest-api/endpoints/class-wp-rest-sidebars-controller.php
index 50c84f1dd9..18dcc4e9c0 100644
--- a/wp-includes/rest-api/endpoints/class-wp-rest-sidebars-controller.php
+++ b/wp-includes/rest-api/endpoints/class-wp-rest-sidebars-controller.php
@@ -281,7 +281,7 @@ class WP_REST_Sidebars_Controller extends WP_REST_Controller {
 
 			$sidebar['status']        = 'active';
 			$sidebar['name']          = isset( $registered_sidebar['name'] ) ? $registered_sidebar['name'] : '';
-			$sidebar['description']   = isset( $registered_sidebar['description'] ) ? $registered_sidebar['description'] : '';
+			$sidebar['description']   = isset( $registered_sidebar['description'] ) ? wp_sidebar_description( $id ) : '';
 			$sidebar['class']         = isset( $registered_sidebar['class'] ) ? $registered_sidebar['class'] : '';
 			$sidebar['before_widget'] = isset( $registered_sidebar['before_widget'] ) ? $registered_sidebar['before_widget'] : '';
 			$sidebar['after_widget']  = isset( $registered_sidebar['after_widget'] ) ? $registered_sidebar['after_widget'] : '';
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 54deb313ea..4590efc690 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51405';
+$wp_version = '5.9-alpha-51408';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.