--- xen-4.5.1/tools/qemu-xen-traditional/vnc.c.orig	2015-07-12 21:55:32.875504811 +0100
+++ xen-4.5.1/tools/qemu-xen-traditional/vnc.c	2015-07-12 22:03:03.860005391 +0100
@@ -2140,7 +2140,7 @@
     GNUTLS_VERSION_NUMBER >= 0x020200 /* 2.2.0 */
 static int vnc_set_gnutls_priority(gnutls_session_t s, int x509)
 {
-    const char *priority = x509 ? "NORMAL" : "NORMAL:+ANON-DH";
+    const char *priority = x509 ? "@SYSTEM" : "@SYSTEM:+ANON-DH";
     int rc;
 
     rc = gnutls_priority_set_direct(s, priority, NULL);