diff --git a/include/etl/message_broker.h b/include/etl/message_broker.h
index 1a3fe11e..74c7f631 100644
--- a/include/etl/message_broker.h
+++ b/include/etl/message_broker.h
@@ -151,6 +151,7 @@ namespace etl
       : imessage_router(id_)
       , head()
     {
+      ETL_ASSERT((id_ <= etl::imessage_router::MAX_MESSAGE_ROUTER) || (id_ == etl::imessage_router::MESSAGE_BROKER), ETL_ERROR(etl::message_router_illegal_id));
     }
 
     //*******************************************
diff --git a/test/test_message_bus.cpp b/test/test_message_bus.cpp
index f002f63c..9407ee36 100644
--- a/test/test_message_bus.cpp
+++ b/test/test_message_bus.cpp
@@ -224,12 +224,35 @@ namespace
     int message_unknown_count;
   };
 
-  SUITE(test_message_router)
+  //***************************************************************************
+  template <size_t Size>
+  class MessageBus : public etl::message_bus<Size>
+  {
+  public:
+
+    MessageBus()
+      : message_count(0)
+    {
+    }
+
+    using etl::message_bus<Size>::receive;
+
+    // Hook 'receive' to count the incomimg messages.
+    void receive(etl::message_router_id_t id, const etl::imessage& msg)
+    {
+      ++message_count;
+      etl::message_bus<Size>::receive(id, msg);
+    }
+
+    int message_count;
+  };
+
+  SUITE(test_message_bus)
   {
     //*************************************************************************
     TEST(message_bus_subscribe_unsubscribe)
     {
-      etl::message_bus<2> bus1;
+      MessageBus<2> bus1;
 
       RouterA router1(0);
       RouterB router2(1);
@@ -260,14 +283,16 @@ namespace
       // Erase router from empty list.
       bus1.unsubscribe(router2);
       CHECK_EQUAL(0U, bus1.size());
+
+      CHECK_EQUAL(0, bus1.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_subscribe_unsubscribe_sub_bus)
     {
-      etl::message_bus<4> bus1;
-      etl::message_bus<2> bus2;
-      etl::message_bus<3> bus3;
+      MessageBus<4> bus1;
+      MessageBus<2> bus2;
+      MessageBus<3> bus3;
 
       RouterA router1(ROUTER1);
       RouterA router2(ROUTER2);
@@ -289,12 +314,16 @@ namespace
 
       bus1.unsubscribe(etl::imessage_bus::ALL_MESSAGE_ROUTERS);
       CHECK_EQUAL(0U, bus1.size());
+
+      CHECK_EQUAL(0, bus1.message_count);
+      CHECK_EQUAL(0, bus2.message_count);
+      CHECK_EQUAL(0, bus3.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_broadcast)
     {
-      etl::message_bus<2> bus1;
+      MessageBus<2> bus1;
 
       RouterA router1(ROUTER1);
       RouterB router2(ROUTER2);
@@ -376,12 +405,14 @@ namespace
       CHECK_EQUAL(0, router2.message_unknown_count);
 
       CHECK_EQUAL(7, callback.message5_count);
+
+      CHECK_EQUAL(4, bus1.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_broadcast_as_router)
     {
-      etl::message_bus<2> bus1;
+      MessageBus<2> bus1;
 
       RouterA router1(ROUTER1);
       RouterB router2(ROUTER2);
@@ -466,12 +497,14 @@ namespace
       CHECK_EQUAL(0, router2.message_unknown_count);
 
       CHECK_EQUAL(7, callback.message5_count);
+
+      CHECK_EQUAL(4, bus1.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_addressed)
     {
-      etl::message_bus<2> bus1;
+      MessageBus<2> bus1;
 
       RouterA router1(ROUTER1);
       RouterB router2(ROUTER2);
@@ -571,12 +604,14 @@ namespace
       CHECK_EQUAL(0, router2.message_unknown_count);
 
       CHECK_EQUAL(4, callback.message5_count);
+      
+      CHECK_EQUAL(5, bus1.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_addressed_duplicate_router_id)
     {
-      etl::message_bus<3> bus1;
+      MessageBus<3> bus1;
 
       RouterA router1(ROUTER1);
       RouterB router2(ROUTER1);
@@ -613,13 +648,15 @@ namespace
       CHECK_EQUAL(0, router3.message_unknown_count);
 
       CHECK_EQUAL(2, callback.message5_count);
+
+      CHECK_EQUAL(1, bus1.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_broadcast_addressed_sub_bus)
     {
-      etl::message_bus<3> bus1;
-      etl::message_bus<2> bus2;
+      MessageBus<3> bus1;
+      MessageBus<2> bus2;
 
       RouterA router1(ROUTER1);
       RouterA router2(ROUTER2);
@@ -729,14 +766,17 @@ namespace
       CHECK_EQUAL(0, router4.message_unknown_count);
 
       CHECK_EQUAL(6, callback.message5_count);
+
+      CHECK_EQUAL(3, bus1.message_count);
+      CHECK_EQUAL(3, bus2.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_broadcast_order)
     {
-      etl::message_bus<4> bus1;
-      etl::message_bus<2> bus2;
-      etl::message_bus<2> bus3;
+      MessageBus<4> bus1;
+      MessageBus<2> bus2;
+      MessageBus<2> bus3;
 
       RouterA router1(ROUTER1);
       RouterA router2(ROUTER2);
@@ -766,13 +806,17 @@ namespace
       CHECK_EQUAL(2, router4b.order);
       CHECK_EQUAL(3, router4a.order);
       CHECK_EQUAL(4, router3.order);
+
+      CHECK_EQUAL(1, bus1.message_count);
+      CHECK_EQUAL(1, bus2.message_count);
+      CHECK_EQUAL(1, bus3.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_broadcast_addressed_successor_bus)
     {
-      etl::message_bus<3> bus1;
-      etl::message_bus<2> bus2;
+      MessageBus<3> bus1;
+      MessageBus<2> bus2;
 
       RouterA router1(ROUTER1);
       RouterA router2(ROUTER2);
@@ -882,12 +926,15 @@ namespace
       CHECK_EQUAL(0, router4.message_unknown_count);
 
       CHECK_EQUAL(6, callback.message5_count);
+
+      CHECK_EQUAL(3, bus1.message_count);
+      CHECK_EQUAL(3, bus2.message_count);
     }
 
     //*************************************************************************
     TEST(message_bus_successor_to_message_producer)
     {
-      etl::message_bus<2> bus;
+      MessageBus<2> bus;
       etl::message_producer producer(ROUTER2);
       RouterA router(ROUTER1);
       Response message;
@@ -901,6 +948,8 @@ namespace
       producer.receive(message);
 
       CHECK_EQUAL(1U, router.message5_count);
+
+      CHECK_EQUAL(1, bus.message_count);
     }
   };
 }