diff --git a/libxml.h b/libxml.h
index 4fe56d2..2efa704 100644
--- a/libxml.h
+++ b/libxml.h
@@ -96,7 +96,7 @@
 #endif
 
 XMLPUBFUN xmlChar * XMLCALL xmlEscapeFormatString(xmlChar **msg);
-int xmlNop(void);
+int xmlInputReadCallbackNop(void *context, char *buffer, int len);
 
 #ifdef IN_LIBXML
 #ifdef __GNUC__
diff --git a/parser.c b/parser.c
index 1c5e036..515ced5 100644
--- a/parser.c
+++ b/parser.c
@@ -2086,7 +2086,8 @@
 
     if (((curEnd > (unsigned long) XML_MAX_LOOKUP_LIMIT) ||
          (curBase > (unsigned long) XML_MAX_LOOKUP_LIMIT)) &&
-         ((ctxt->input->buf) && (ctxt->input->buf->readcallback != (xmlInputReadCallback) xmlNop)) &&
+         ((ctxt->input->buf) &&
+          (ctxt->input->buf->readcallback != xmlInputReadCallbackNop)) &&
         ((ctxt->options & XML_PARSE_HUGE) == 0)) {
         xmlFatalErr(ctxt, XML_ERR_INTERNAL_ERROR, "Huge input lookup");
         xmlHaltParser(ctxt);
diff --git a/xmlIO.c b/xmlIO.c
index 0fd8c49..1d49095 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -703,14 +703,16 @@
 }
 
 /**
- * xmlNop:
+ * xmlInputReadCallbackNop:
  *
- * No Operation function, does nothing, no input
+ * No Operation xmlInputReadCallback function, does nothing.
  *
  * Returns zero
  */
 int
-xmlNop(void) {
+xmlInputReadCallbackNop(void *context ATTRIBUTE_UNUSED,
+                        char *buffer ATTRIBUTE_UNUSED,
+                        int len ATTRIBUTE_UNUSED) {
     return(0);
 }
 
@@ -2932,7 +2934,7 @@
     ret = xmlAllocParserInputBuffer(enc);
     if (ret != NULL) {
         ret->context = (void *) mem;
-	ret->readcallback = (xmlInputReadCallback) xmlNop;
+	ret->readcallback = xmlInputReadCallbackNop;
 	ret->closecallback = NULL;
 	errcode = xmlBufAdd(ret->buffer, (const xmlChar *) mem, size);
 	if (errcode != 0) {