diff --git a/include/etl/message_router.h b/include/etl/message_router.h
index 7073f38c..70a1607a 100644
--- a/include/etl/message_router.h
+++ b/include/etl/message_router.h
@@ -418,18 +418,28 @@ namespace etl
     message_router()
       : imessage_router(etl::imessage_router::MESSAGE_ROUTER)
     {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived, TMessageTypes...>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived, TMessageTypes...>");
     }
 
     //**********************************************
     message_router(etl::imessage_router& successor_)
       : imessage_router(etl::imessage_router::MESSAGE_ROUTER, successor_)
     {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived, TMessageTypes...>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived, TMessageTypes...>");
     }
 
     //**********************************************
     message_router(etl::message_router_id_t id_)
       : imessage_router(id_)
     {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived, TMessageTypes...>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived, TMessageTypes...>");
+
       ETL_ASSERT(id_ <= etl::imessage_router::MAX_MESSAGE_ROUTER, ETL_ERROR(etl::message_router_illegal_id));
     }
 
@@ -437,6 +447,10 @@ namespace etl
     message_router(etl::message_router_id_t id_, etl::imessage_router& successor_)
       : imessage_router(id_, successor_)
     {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived, TMessageTypes...>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived, TMessageTypes...>");
+
       ETL_ASSERT(id_ <= etl::imessage_router::MAX_MESSAGE_ROUTER, ETL_ERROR(etl::message_router_illegal_id));
     }
 
@@ -551,6 +565,106 @@ namespace etl
     }
   };
 
+  //***************************************************************************
+  // The definition for all message types.
+  //***************************************************************************
+  template <typename TDerived>
+  class message_router<TDerived> : public imessage_router
+  {
+  public:
+
+    using message_packet = etl::message_packet<>;
+    using message_types  = etl::type_list<>;
+
+    //**********************************************
+    message_router()
+      : imessage_router(etl::imessage_router::MESSAGE_ROUTER)
+    {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived>");
+    }
+
+    //**********************************************
+    message_router(etl::imessage_router& successor_)
+      : imessage_router(etl::imessage_router::MESSAGE_ROUTER, successor_)
+    {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived>");
+    }
+
+    //**********************************************
+    message_router(etl::message_router_id_t id_)
+      : imessage_router(id_)
+    {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived>");
+
+      ETL_ASSERT(id_ <= etl::imessage_router::MAX_MESSAGE_ROUTER, ETL_ERROR(etl::message_router_illegal_id));
+    }
+
+    //**********************************************
+    message_router(etl::message_router_id_t id_, etl::imessage_router& successor_)
+      : imessage_router(id_, successor_)
+    {
+      // CRTP validation: Derived must inherit from this exact specialization.
+      ETL_STATIC_ASSERT((etl::is_base_of<etl::message_router<TDerived>, TDerived>::value),
+                        "Mismatch in derived type: TDerived does not inherit from etl::message_router<TDerived>");
+
+      ETL_ASSERT(id_ <= etl::imessage_router::MAX_MESSAGE_ROUTER, ETL_ERROR(etl::message_router_illegal_id));
+    }
+
+    //**********************************************
+    using etl::imessage_router::receive;
+
+    void receive(const etl::imessage& msg) ETL_OVERRIDE
+    {
+      if (has_successor())
+      {
+        get_successor().receive(msg);
+      }
+    }
+
+    template <typename TMessage, typename etl::enable_if<etl::is_base_of<imessage, TMessage>::value, int>::type = 0>
+    void receive(const TMessage& msg)
+    {
+#include "etl/private/diagnostic_array_bounds_push.h"
+      if (has_successor())
+      {
+        get_successor().receive(msg);
+      }
+#include "etl/private/diagnostic_pop.h"
+    }
+
+    //**********************************************
+    using imessage_router::accepts;
+
+    bool accepts(etl::message_id_t id) const ETL_OVERRIDE
+    {
+      return false;
+    }
+
+    //********************************************
+    ETL_DEPRECATED bool is_null_router() const ETL_OVERRIDE
+    {
+      return false;
+    }
+
+    //********************************************
+    bool is_producer() const ETL_OVERRIDE
+    {
+      return true;
+    }
+
+    //********************************************
+    bool is_consumer() const ETL_OVERRIDE
+    {
+      return true;
+    }
+  };
+
   //***************************************************************************
   /// Helper to turn etl::type_list<TTypes...> into etl::tuple<TTypes...>
   template <typename TDerived, typename TList>
diff --git a/test/test_message_router.cpp b/test/test_message_router.cpp
index 53da2b6b..2413d067 100644
--- a/test/test_message_router.cpp
+++ b/test/test_message_router.cpp
@@ -49,6 +49,7 @@ namespace
 
   enum
   {
+    ROUTER0,
     ROUTER1,
     ROUTER2,
     ROUTER3
@@ -119,17 +120,26 @@ namespace
 
   Message5 message5;
 
+  //***************************************************************************
+  // Router that handles no messages.
+  //***************************************************************************
+  class Router0 : public etl::message_router<Router0>
+  {
+  public:
+
+    Router0()
+      : message_router(ROUTER0)
+    {
+    }
+  };
+
   //***************************************************************************
   // Router that handles messages 1, 2, 3, 4 and 5 and returns nothing.
   // Created from a type list.
   //***************************************************************************
-#if ETL_USING_CPP17 && !defined(ETL_MESSAGE_ROUTER_FORCE_CPP03_IMPLEMENTATION)
   using Router1Messages = etl::type_list<Message1, Message2, Message3, Message4, Message5>;
 
   class Router1 : public etl::message_router_from_type_list_t<Router1, Router1Messages>
-#else
-  class Router1 : public etl::message_router<Router1, Message1, Message2, Message3, Message4, Message5>
-#endif
   {
   public:
 
@@ -384,6 +394,84 @@ namespace
       CHECK_EQUAL(4, r2.callback_count);
     }
 
+    //*************************************************************************
+    TEST(message_router_with_no_message_types)
+    {
+      Router0 r0;
+      Router1 r1;
+      Router2 r2;
+
+      Message1 message1(r2);
+      Message2 message2(r2);
+      Message3 message3(r2);
+      Message4 message4(r2);
+
+      r0.append_successor(r1); // All messages are passed to r1.
+
+      CHECK_TRUE((etl::is_same<Router0::message_types, etl::type_list<>>::value));
+
+      CHECK(!r0.is_null_router());
+      CHECK(r0.is_producer());
+      CHECK(r0.is_consumer());
+
+      r1.receive(message1);
+      CHECK_EQUAL(1, r1.message1_count);
+      CHECK_EQUAL(0, r1.message2_count);
+      CHECK_EQUAL(0, r1.message3_count);
+      CHECK_EQUAL(0, r1.message4_count);
+      CHECK_EQUAL(0, r1.message_unknown_count);
+      CHECK_EQUAL(1, r2.callback_count);
+
+      r1.receive(message2);
+      CHECK_EQUAL(1, r1.message1_count);
+      CHECK_EQUAL(1, r1.message2_count);
+      CHECK_EQUAL(0, r1.message3_count);
+      CHECK_EQUAL(0, r1.message4_count);
+      CHECK_EQUAL(0, r1.message_unknown_count);
+      CHECK_EQUAL(2, r2.callback_count);
+
+      r1.receive(message3);
+      CHECK_EQUAL(1, r1.message1_count);
+      CHECK_EQUAL(1, r1.message2_count);
+      CHECK_EQUAL(1, r1.message3_count);
+      CHECK_EQUAL(0, r1.message4_count);
+      CHECK_EQUAL(0, r1.message_unknown_count);
+      CHECK_EQUAL(3, r2.callback_count);
+
+      r1.receive(message4);
+      CHECK_EQUAL(1, r1.message1_count);
+      CHECK_EQUAL(1, r1.message2_count);
+      CHECK_EQUAL(1, r1.message3_count);
+      CHECK_EQUAL(1, r1.message4_count);
+      CHECK_EQUAL(0, r1.message_unknown_count);
+      CHECK_EQUAL(4, r2.callback_count);
+
+      //// Send from the null router.
+      //etl::send_message(r0, message1);
+      //CHECK_EQUAL(1, r2.message1_count);
+      //CHECK_EQUAL(0, r2.message2_count);
+      //CHECK_EQUAL(0, r2.message4_count);
+      //CHECK_EQUAL(0, r2.message_unknown_count);
+
+      //etl::send_message(r0, message2);
+      //CHECK_EQUAL(1, r2.message1_count);
+      //CHECK_EQUAL(1, r2.message2_count);
+      //CHECK_EQUAL(0, r2.message4_count);
+      //CHECK_EQUAL(0, r2.message_unknown_count);
+
+      //etl::send_message(r0, message3);
+      //CHECK_EQUAL(1, r2.message1_count);
+      //CHECK_EQUAL(1, r2.message2_count);
+      //CHECK_EQUAL(0, r2.message4_count);
+      //CHECK_EQUAL(1, r2.message_unknown_count);
+
+      //etl::send_message(r0, message4);
+      //CHECK_EQUAL(1, r2.message1_count);
+      //CHECK_EQUAL(1, r2.message2_count);
+      //CHECK_EQUAL(1, r2.message4_count);
+      //CHECK_EQUAL(1, r2.message_unknown_count);
+    }
+
     //*************************************************************************
     TEST(message_null_router)
     {