diff --git a/libvncclient/sockets.c b/libvncclient/sockets.c
index a4caaa5..334928e 100644
--- a/libvncclient/sockets.c
+++ b/libvncclient/sockets.c
@@ -599,7 +599,7 @@ SetDSCP(int sock, int dscp)
 
   switch(addr.sa_family)
     {
-#ifdef LIBVNCSERVER_IPv6
+#if defined LIBVNCSERVER_IPv6 && defined IPV6_TCLASS
     case AF_INET6:
       level = IPPROTO_IPV6;
       cmd = IPV6_TCLASS;