diff --git a/xmlIO.h b/xmlIO.h
index 58baeb0..2bdba5d 100644
--- a/xmlIO.h
+++ b/xmlIO.h
@@ -52,7 +52,7 @@
 						 int len);
 int	xmlParserInputBufferPush		(xmlParserInputBufferPtr in,
 						 int len,
-						 char *buf);
+						 const char *buf);
 void	xmlFreeParserInputBuffer		(xmlParserInputBufferPtr in);
 char *	xmlParserGetDirectory			(const char *filename);