diff --git a/c14n.c b/c14n.c
index 25d9b9c..83eee10 100644
--- a/c14n.c
+++ b/c14n.c
@@ -9,6 +9,7 @@
  * 
  * Author: Aleksey Sanin <aleksey@aleksey.com>
  */
+#define IN_LIBXML
 #include "libxml.h"
 #ifdef LIBXML_C14N_ENABLED