Ticket #21978: 21978.patch

wp-includes/class-wp.php

@@ -505 +505 @@
                         }
                 }
 
+                // Let plugins hook in and possibly abort the 404
+                do_action( 'pre_send_404_header' );
+
                 // Guess it's time to 404.
                 $wp_query->set_404();
                 status_header( 404 );