--- a/src/internet/model/global-route-manager-impl.cc	Thu May 16 11:18:20 2013 -0400
+++ b/src/internet/model/global-route-manager-impl.cc	Thu May 16 11:25:29 2013 -0400
@@ -837,6 +837,7 @@
 //
       if (v->GetLSA ()->GetLSType () == GlobalRoutingLSA::RouterLSA)
         {
+          NS_ASSERT (l != 0);
           distance = v->GetDistanceFromRoot () + l->GetMetric ();
         }
       else