diff --git a/src/wp-admin/includes/upgrade.php b/src/wp-admin/includes/upgrade.php
index 54188738df..2af5946558 100644
--- a/src/wp-admin/includes/upgrade.php
+++ b/src/wp-admin/includes/upgrade.php
@@ -2261,6 +2261,8 @@ function upgrade_560() {
  *
  * @ignore
  * @since 5.9.0
+ *
+ * @global int $wp_current_db_version The old (current) database version.
  */
 function upgrade_590() {
 	global $wp_current_db_version;