diff --git a/lib/http.h b/lib/http.h
index d78322ce5b6133e5cd7bb6c208ab6a35d8b2eaa5..2f40ea1ff28feedc504cc48395ab82c495ba6c54 100644
--- a/lib/http.h
+++ b/lib/http.h
@@ -24,6 +24,10 @@
  * $Id$
  ***************************************************************************/
 #ifndef CURL_DISABLE_HTTP
+bool Curl_compareheader(char *headerline,     /* line to check */
+                        const char *header,   /* header keyword _with_ colon */
+                        const char *content); /* content string to find */
+
 /* ftp can use this as well */
 CURLcode Curl_ConnectHTTPProxyTunnel(struct connectdata *conn,
                                      int tunnelsocket,