diff --git a/xinclude.c b/xinclude.c
index ff3dafb..e3bb43e 100644
--- a/xinclude.c
+++ b/xinclude.c
@@ -125,7 +125,7 @@
  *
  * Handle an XInclude error
  */
-static void
+static void LIBXML_ATTR_FORMAT(4,0)
 xmlXIncludeErr(xmlXIncludeCtxtPtr ctxt, xmlNodePtr node, int error,
                const char *msg, const xmlChar *extra)
 {
@@ -147,7 +147,7 @@
  *
  * Emit an XInclude warning.
  */
-static void
+static void LIBXML_ATTR_FORMAT(4,0)
 xmlXIncludeWarn(xmlXIncludeCtxtPtr ctxt, xmlNodePtr node, int error,
                const char *msg, const xmlChar *extra)
 {