Index: src/wp-includes/comment.php
===================================================================
--- src/wp-includes/comment.php	(revision 41352)
+++ src/wp-includes/comment.php	(working copy)
@@ -2550,6 +2550,8 @@
  *
  * @param string $content Post content to check for links. If empty will retrieve from post.
  * @param int|WP_Post $post_id Post Object or ID.
+ *
+ * @return bool True on success, false if no post is available for the given ID.
  */
 function pingback( $content, $post_id ) {
 	include_once( ABSPATH . WPINC . '/class-IXR.php' );
@@ -2560,7 +2562,7 @@
 
 	$post = get_post( $post_id );
 	if ( ! $post ) {
-		return;
+		return false;
 	}
 
 	$pung = get_pung( $post );
@@ -2637,6 +2639,8 @@
 				add_ping( $post, $pagelinkedto );
 		}
 	}
+
+	return true;
 }
 
 /**