diff -r 4ddd95a4b74f -r bef75e0d0487 src/mem/bus.cc
--- a/src/mem/bus.cc	Fri Dec 16 15:32:42 2011 -0600
+++ b/src/mem/bus.cc	Fri Dec 16 15:32:55 2011 -0600
@@ -257,6 +257,11 @@
             defaultPort : interfaces[dest_port_id];
     }
 
+    if (dest_port == NULL) {
+        fatal("%s: dest_port NULL for pkt: src %d, dst %d, %s, addr:0x%x\n",
+              name(), src, pkt->getDest(), pkt->cmdString(), pkt->getAddr());
+    }
+
     if (dest_port_id == src) {
         // Must be forwarded snoop up from below...
         assert(dest == Packet::Broadcast);