Index: src/wp-admin/includes/meta-boxes.php
===================================================================
--- src/wp-admin/includes/meta-boxes.php	(revision 40289)
+++ src/wp-admin/includes/meta-boxes.php	(working copy)
@@ -651,7 +651,7 @@
 	printf(
 		/* translators: %s: Codex URL */
 		__( 'Custom fields can be used to add extra metadata to a post that you can <a href="%s">use in your theme</a>.' ),
-		__( 'https://codex.wordpress.org/Using_Custom_Fields' )
+		__( 'https://codex.wordpress.org/Custom_Fields' )
 	);
 ?></p>
 <?php