diff --git a/src/wp-includes/class-wp-xmlrpc-server.php b/src/wp-includes/class-wp-xmlrpc-server.php
index 5a67096d0a..59a7c226f0 100644
--- a/src/wp-includes/class-wp-xmlrpc-server.php
+++ b/src/wp-includes/class-wp-xmlrpc-server.php
@@ -6210,6 +6210,8 @@ class wp_xmlrpc_server extends IXR_Server {
 	 * @return string|IXR_Error
 	 */
 	public function pingback_ping( $args ) {
+		global $wpdb;
+
 		/** This action is documented in wp-includes/class-wp-xmlrpc-server.php */
 		do_action( 'xmlrpc_call', 'pingback.ping' );