diff --git a/istl/localindex.hh b/istl/localindex.hh
index 961a6da430e4790b5df532613ef52f2da86a619e..6111db2ace1feb197a433d9b73df47b8e76b3305 100644
--- a/istl/localindex.hh
+++ b/istl/localindex.hh
@@ -2,10 +2,11 @@
 // vi: set et ts=4 sw=2 sts=2:
 // $Id$
 
-#ifndef DUNE_LOCALINDEX_HH
-#define DUNE_LOCALINDEX_HH
+#ifndef DUNE_ISTL_LOCALINDEX_HH
+#define DUNE_ISTL_LOCALINDEX_HH
 
 #include "config.h"
+#include <cstddef>
 
 namespace Dune
 {