Ticket #30970: 30970.2.patch

src/wp-includes/query.php

@@ -4568 +4568 @@
          *
          * @since 4.1.0
          *
-         * @param WP_Post $post Post data.
+         * @param WP_Post $p Post data or post ID.
          * @return bool True when finished.
          */
         public function setup_postdata( $post ) {
                 global $id, $authordata, $currentday, $currentmonth, $page, $pages, $multipage, $more, $numpages;
 
+                if ( ! ( $post instanceof WP_Post ) ) {
+                        $post = get_post( $post );
+                }
+
                 $id = (int) $post->ID;
 
                 $authordata = get_userdata($post->post_author);