diff --git a/src/traction_modem/Link.cxxtest b/src/traction_modem/Link.cxxtest
index ffa6f0b7d..4365641c2 100644
--- a/src/traction_modem/Link.cxxtest
+++ b/src/traction_modem/Link.cxxtest
@@ -298,6 +298,7 @@ TEST_F(LinkTest, LinkUpMaxDelay)
         Defs::append_uint8(&b->data()->payload, 0);
         Defs::append_uint8(&b->data()->payload, 0);
         Defs::append_crc(&b->data()->payload);
+        mRxFlow_.trigger_packet_rx_callback();
         static_cast<PacketFlowInterface*>(&linkManager_)->send(b);
         wait_for_main_executor();
         testing::Mock::VerifyAndClearExpectations(&mTxFlow_);
diff --git a/src/traction_modem/Link.hxx b/src/traction_modem/Link.hxx
index 1757e8f70..2ac7bf563 100644
--- a/src/traction_modem/Link.hxx
+++ b/src/traction_modem/Link.hxx
@@ -205,6 +205,8 @@ public:
         , useDefaultBaud_(use_default_baud)
     {
         link_->register_link_status(this);
+        link_->get_rx_iface()->register_packet_rx_callback(
+            std::bind(&LinkManager::packet_rx_callback, this));
     }
 
 #if defined(GTEST)
@@ -227,6 +229,19 @@ private:
     /// Alias for short response timeout used during link establishment.
     static constexpr long long RESP_TIMEOUT = Defs::RESP_TIMEOUT_SHORT;
 
+    // Callback for when any packet is received.
+    void packet_rx_callback()
+    {
+        if (link_->is_link_up())
+        {
+            // Note: link_is_down() is technically the "next" state, if
+            //       the link fails (timer_ expires without pong).
+            HASSERT(is_state(STATE(link_is_down)));
+            // Everything is good, don't trigger an early timer_ wakeup.
+            timer_.restart();
+        }
+    }
+
     /// Called when the link is started.
     void on_link_start() override
     {
@@ -338,14 +353,10 @@ private:
         switch(buf->data()->command())
         {
             case Defs::RESP_PING:
+                /// @todo This is a good place to extract the revision info.
                 if (link_->is_link_up())
                 {
-                    // Note: link_is_down() is technically the "next" state, if
-                    //       the link fails (timer_ expires without pong).
-                    HASSERT(is_state(STATE(link_is_down)));
-                    // Everything is good, don't trigger an early timer_ wakeup.
-                    timer_.restart();
-                    return; 
+                    return;
                 }
                 break;
             case Defs::RESP_BAUD_RATE_QUERY:
diff --git a/src/traction_modem/RxFlow.hxx b/src/traction_modem/RxFlow.hxx
index d2e7940cb..947aabd54 100644
--- a/src/traction_modem/RxFlow.hxx
+++ b/src/traction_modem/RxFlow.hxx
@@ -83,9 +83,18 @@ public:
     {
         return resyncCount_;
     }
+
+    /// Register for a callback when any packet is received.
+    virtual void register_packet_rx_callback(std::function<void()> callback)
+    {
+        pktRxCallback_ = callback;
+    }
+
 protected:
     /// Track the number of times that we try to resync.
     unsigned resyncCount_{0};
+    /// Callback for when any packet is received.
+    std::function<void()> pktRxCallback_;
 };
 
 /// Object responsible for reading in a stream of bytes over the modem
@@ -323,6 +332,10 @@ private:
 
         auto *b = dispatcher_.alloc();
         b->data()->payload = std::move(payload_);
+        if (pktRxCallback_)
+        {
+            pktRxCallback_();
+        }
         dispatcher_.send(b);
 
         if (payload_tmp.size())
diff --git a/src/traction_modem/modem_test_helper.hxx b/src/traction_modem/modem_test_helper.hxx
index 10ca513ab..09deaabfd 100644
--- a/src/traction_modem/modem_test_helper.hxx
+++ b/src/traction_modem/modem_test_helper.hxx
@@ -19,6 +19,14 @@ public:
         void(PacketFlowInterface*, Message::id_type, Message::id_type));
     MOCK_METHOD1(unregister_handler_all, void(PacketFlowInterface*));
     MOCK_METHOD1(register_fallback_handler, void(PacketFlowInterface*));
+
+    void trigger_packet_rx_callback()
+    {
+        if (pktRxCallback_)
+        {
+            pktRxCallback_();
+        }
+    }
 };
 
 class MyMockRxFlow : public MockRxFlow
@@ -104,6 +112,7 @@ protected:
                     Defs::append_uint8(&b->data()->payload, 0);
                     Defs::append_uint8(&b->data()->payload, 0);
                     Defs::append_crc(&b->data()->payload);
+                    mRxFlow_.trigger_packet_rx_callback();
                     static_cast<PacketFlowInterface*>(&linkManager_)->send(b);
                 }
             }
@@ -147,6 +156,7 @@ protected:
             Defs::append_uint8(&b->data()->payload, 0);
             Defs::append_uint8(&b->data()->payload, 0);
             Defs::append_crc(&b->data()->payload);
+            mRxFlow_.trigger_packet_rx_callback();
             static_cast<PacketFlowInterface*>(&linkManager_)->send(b);
             wait_for_main_executor();
             EXPECT_TRUE(link_.is_link_up());