diff --git a/opentracker.c b/opentracker.c
index 6747978..41fe013 100644
--- a/opentracker.c
+++ b/opentracker.c
@@ -2,7 +2,7 @@
    It is considered beerware. Prost. Skol. Cheers or whatever.
    Some of the stuff below is stolen from Fefes example libowfat httpd.
 
-   $Id: opentracker.c,v 1.210 2009/01/13 22:41:16 erdgeist Exp $ */
+   $Id: opentracker.c,v 1.211 2009/01/15 16:20:47 erdgeist Exp $ */
 
 /* System */
 #include <stdlib.h>
@@ -238,6 +238,16 @@ static void server_mainloop( ) {
 static int64_t ot_try_bind( ot_ip6 ip, uint16_t port, PROTO_FLAG proto ) {
   int64 s = proto == FLAG_TCP ? socket_tcp6( ) : socket_udp6( );
 
+#ifndef WANT_V6
+  if( !ip6_isv4mapped(ip) ) {
+    exerr( "V4 Tracker is V4 only!" );
+  }
+#else
+  if( ip6_isv4mapped(ip) ) {
+    exerr( "V6 Tracker is V6 only!" );
+  }  
+#endif
+
 #ifdef _DEBUG
   char *protos[] = {"TCP","UDP","UDP mcast"};
   char _debug[512];
@@ -420,6 +430,9 @@ int main( int argc, char **argv ) {
   uint16_t tmpport;
 
   memset( serverip, 0, sizeof(ot_ip6) );
+#ifndef WANT_V6
+  serverip[10]=serverip[11]=0xff;
+#endif
 
 while( scanon ) {
     switch( getopt( argc, argv, ":i:p:A:P:d:r:s:f:v"
@@ -494,4 +507,4 @@ while( scanon ) {
   return 0;
 }
 
-const char *g_version_opentracker_c = "$Source: /home/cvsroot/opentracker/opentracker.c,v $: $Revision: 1.210 $\n";
+const char *g_version_opentracker_c = "$Source: /home/cvsroot/opentracker/opentracker.c,v $: $Revision: 1.211 $\n";