Index: wp-includes/post.php
===================================================================
--- wp-includes/post.php	(revision 24405)
+++ wp-includes/post.php	(working copy)
@@ -3554,15 +3554,18 @@
  * @since 1.5.0
  *
  * @param mixed $page Page object or page ID.
- * @return string Page URI.
+ * @return string|false Page URI, false on error.
  */
 function get_page_uri($page) {
 	$page = get_post( $page );
 
+	if ( ! $page )
+		return false;
+
 	$uri = $page->post_name;
 
 	foreach ( $page->ancestors as $parent ) {
-		$uri = get_post( $parent )->post_name . "/" . $uri;
+		$uri = get_post( $parent )->post_name . '/' . $uri;
 	}
 
 	return $uri;