Index: src/wp-includes/post.php
===================================================================
--- src/wp-includes/post.php	(revision 45717)
+++ src/wp-includes/post.php	(working copy)
@@ -6315,7 +6315,7 @@
 
 	$lastpostmodified = _get_last_post_time( $timezone, 'modified', $post_type );
 
-	$lastpostdate = get_lastpostdate( $timezone );
+	$lastpostdate = get_lastpostdate( $timezone, $post_type );
 	if ( $lastpostdate > $lastpostmodified ) {
 		$lastpostmodified = $lastpostdate;
 	}
@@ -6328,8 +6328,9 @@
 	 * @param string $lastpostmodified Date the last post was modified.
 	 * @param string $timezone         Location to use for getting the post modified date.
 	 *                                 See get_lastpostdate() for accepted `$timezone` values.
+	 * @param string $post_type        The post type to check.
 	 */
-	return apply_filters( 'get_lastpostmodified', $lastpostmodified, $timezone );
+	return apply_filters( 'get_lastpostmodified', $lastpostmodified, $timezone, $post_type );
 }
 
 /**