1 files changed, 16 insertions, 1 deletions
diff --git a/valid.c b/valid.c
index 18a1fde..15514d8 100644
--- a/valid.c
+++ b/valid.c
@@ -18,6 +18,7 @@
 
 #include <libxml/xmlmemory.h>
 #include <libxml/hash.h>
+#include <libxml/uri.h>
 #include <libxml/valid.h>
 #include <libxml/parser.h>
 #include <libxml/parserInternals.h>
@@ -6502,8 +6503,22 @@ xmlValidateDocument(xmlValidCtxtPtr ctxt, xmlDocPtr doc) {
     }
     if ((doc->intSubset != NULL) && ((doc->intSubset->SystemID != NULL) ||
 	(doc->intSubset->ExternalID != NULL)) && (doc->extSubset == NULL)) {
+	xmlChar *sysID;
+	if (doc->intSubset->SystemID != NULL) {
+	    sysID = xmlBuildURI(doc->intSubset->SystemID,
+	    		doc->URL);
+	    if (sysID == NULL) {
+	        xmlErrValid(ctxt, XML_DTD_LOAD_ERROR,
+			"Could not build URI for external subset \"%s\"\n",
+			(const char *) doc->intSubset->SystemID);
+		return 0;
+	    }
+	} else
+	    sysID = NULL;
         doc->extSubset = xmlParseDTD(doc->intSubset->ExternalID,
-		                     doc->intSubset->SystemID);
+			(const xmlChar *)sysID);
+	if (sysID != NULL)
+	    xmlFree(sysID);
         if (doc->extSubset == NULL) {
 	    if (doc->intSubset->SystemID != NULL) {
 		xmlErrValid(ctxt, XML_DTD_LOAD_ERROR,