diff --git a/include/layout.inc b/include/layout.inc
index 9acd961e3..a8b48b282 100644
--- a/include/layout.inc
+++ b/include/layout.inc
@@ -510,7 +510,7 @@ function clean_note($text)
     // Turn urls into links
     $text = preg_replace(
         '!((mailto:|(http|ftp|nntp|news):\/\/).*?)(\s|<|\)|"|\\\\|\'|$)!',
-        '<a href="\1" target="_blank">\1</a>\4',
+        '<a href="\1" rel="nofollow" target="_blank">\1</a>\4',
         $text
     );