diff --git a/src/mem/packet_queue.cc b/src/mem/packet_queue.cc
index 8030cb38f3..e60e77453b 100644
--- a/src/mem/packet_queue.cc
+++ b/src/mem/packet_queue.cc
@@ -113,6 +113,13 @@ PacketQueue::schedSendTiming(PacketPtr pkt, Tick when, bool send_as_snoop)
     // express snoops should never be queued
     assert(!pkt->isExpressSnoop());
 
+    // add a very basic sanity check on the port to ensure the
+    // invisible buffer is not growing beyond reasonable limits
+    if (transmitList.size() > 100) {
+        panic("Packet queue %s has grown beyond 100 packets\n",
+              name());
+    }
+
     // nothing on the list, or earlier than current front element,
     // schedule an event
     if (transmitList.empty() || when < transmitList.front().tick) {