diff --git a/xpointer.c b/xpointer.c
index 4b4ac2e..676c510 100644
--- a/xpointer.c
+++ b/xpointer.c
@@ -85,7 +85,7 @@
  *
  * Handle a redefinition of attribute error
  */
-static void
+static void LIBXML_ATTR_FORMAT(3,0)
 xmlXPtrErr(xmlXPathParserContextPtr ctxt, int error,
            const char * msg, const xmlChar *extra)
 {