diff --git a/examples/ipv6/rpl-border-router/project-conf.h b/examples/ipv6/rpl-border-router/project-conf.h
index cca0a0e5a..863552544 100644
--- a/examples/ipv6/rpl-border-router/project-conf.h
+++ b/examples/ipv6/rpl-border-router/project-conf.h
@@ -32,19 +32,24 @@
 #ifndef __PROJECT_ROUTER_CONF_H__
 #define __PROJECT_ROUTER_CONF_H__
 
-#undef UIP_FALLBACK_INTERFACE
+#ifndef UIP_FALLBACK_INTERFACE
 #define UIP_FALLBACK_INTERFACE rpl_interface
+#endif
 
-#undef QUEUEBUF_CONF_NUM
+#ifndef QUEUEBUF_CONF_NUM
 #define QUEUEBUF_CONF_NUM          4
+#endif
 
-#undef UIP_CONF_BUFFER_SIZE
+#ifndef UIP_CONF_BUFFER_SIZE
 #define UIP_CONF_BUFFER_SIZE    140
+#endif
 
-#undef UIP_CONF_RECEIVE_WINDOW
+#ifndef UIP_CONF_RECEIVE_WINDOW
 #define UIP_CONF_RECEIVE_WINDOW  60
+#endif
 
-#undef WEBSERVER_CONF_CFS_CONNS
+#ifndef WEBSERVER_CONF_CFS_CONNS
 #define WEBSERVER_CONF_CFS_CONNS 2
+#endif
 
 #endif /* __PROJECT_ROUTER_CONF_H__ */