--- a/libxml.h
+++ b/libxml.h
@@ -96,7 +96,7 @@ int __xmlRandom(void);
 #endif
 
 XMLPUBFUN xmlChar * XMLCALL xmlEscapeFormatString(xmlChar **msg);
-int xmlNop(void);
+int xmlNop(void *context, char *buffer, int len);
 
 #ifdef IN_LIBXML
 #ifdef __GNUC__
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -808,7 +808,7 @@ xmlCheckFilename (const char *path)
  * Returns zero
  */
 int
-xmlNop(void) {
+xmlNop(void *context, char *buffer, int len) {
     return(0);
 }