added IN_LIBXML macro
diff --git a/xmlwriter.c b/xmlwriter.c
index fb5acb4..f427200 100644
--- a/xmlwriter.c
+++ b/xmlwriter.c
@@ -8,6 +8,7 @@
  * alfred@mickautsch.de
  */
 
+#define IN_LIBXML
 #include <string.h>
 
 #include "libxml.h"