diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index bf54ad139..5b2786f05 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -32,7 +32,7 @@
  *
  * This file is part of the Contiki operating system.
  *
- * $Id: rpl-dag.c,v 1.20 2010/06/07 11:36:02 nvt-se Exp $
+ * $Id: rpl-dag.c,v 1.21 2010/06/07 13:40:05 nvt-se Exp $
  */
 /**
  * \file
@@ -545,7 +545,9 @@ rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
     return;
   }
 
-  dag->dtsn = dio->dtsn;
+  if(dag->rank != ROOT_RANK && dag->dtsn < dio->dtsn || dag->dtsn == ~0) {
+    dag->dtsn = dio->dtsn;
+  }
 
   /* This DIO pertains to a DAG that we are already part of. */
   p = rpl_find_parent(dag, from);