--- a/src/internet-stack/arp-cache.cc	Thu May 21 06:04:40 2009 -0700
+++ b/src/internet-stack/arp-cache.cc	Thu May 21 06:07:03 2009 -0700
@@ -33,6 +33,8 @@
 
 namespace ns3 {
 
+NS_OBJECT_ENSURE_REGISTERED (ArpCache);
+
 TypeId 
 ArpCache::GetTypeId (void)
 {