diff --git a/src/fsm.h b/src/fsm.h
index af114f4b..8365d7bf 100644
--- a/src/fsm.h
+++ b/src/fsm.h
@@ -375,7 +375,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -429,7 +429,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -482,7 +482,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -534,7 +534,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -584,7 +584,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -633,7 +633,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -681,7 +681,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -728,7 +728,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -773,7 +773,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -817,7 +817,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -860,7 +860,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -902,7 +902,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -942,7 +942,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -981,7 +981,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -1019,7 +1019,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
@@ -1056,7 +1056,7 @@ namespace etl
     etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)
     {
       etl::fsm_state_id_t new_state_id;
-      etl::message_id_t event_id = message.message_id;
+      etl::message_id_t event_id = message.get_message_id();
 
       switch (event_id)
       {
diff --git a/src/fsm_generator.h b/src/fsm_generator.h
index dde71e15..990bf85a 100644
--- a/src/fsm_generator.h
+++ b/src/fsm_generator.h
@@ -395,7 +395,7 @@ namespace etl
   cog.outl("  etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)")
   cog.outl("  {")
   cog.outl("    etl::fsm_state_id_t new_state_id;")
-  cog.outl("    etl::message_id_t event_id = message.message_id;")
+  cog.outl("    etl::message_id_t event_id = message.get_message_id();")
   cog.outl("")
   cog.outl("    switch (event_id)")
   cog.outl("    {")
@@ -461,7 +461,7 @@ namespace etl
       cog.outl("  etl::fsm_state_id_t process_event(etl::imessage_router& source, const etl::imessage& message)")
       cog.outl("  {")
       cog.outl("    etl::fsm_state_id_t new_state_id;")
-      cog.outl("    etl::message_id_t event_id = message.message_id;")
+      cog.outl("    etl::message_id_t event_id = message.get_message_id();")
       cog.outl("")
       cog.outl("    switch (event_id)")
       cog.outl("    {")
diff --git a/src/message.h b/src/message.h
index ae260796..d422e7b5 100644
--- a/src/message.h
+++ b/src/message.h
@@ -69,16 +69,7 @@ namespace etl
 
     //********************************************
     virtual ~imessage() {}
-
-    const etl::message_id_t message_id;
-
-  protected:
-
-    //********************************************
-    imessage(etl::message_id_t id)
-      : message_id(id)
-    {
-    }
+    virtual etl::message_id_t get_message_id() const = 0;
   };
 
   //***************************************************************************
@@ -93,9 +84,9 @@ namespace etl
     };
 
     //********************************************
-    message()
-      : imessage(ID_)
+    etl::message_id_t get_message_id() const
     {
+      return ID;
     }
   };
 }
diff --git a/src/message_bus.h b/src/message_bus.h
index 44f18761..4be39fca 100644
--- a/src/message_bus.h
+++ b/src/message_bus.h
@@ -219,7 +219,7 @@ namespace etl
               // So pass it on.
               bus.receive(source, destination_router_id, message);
             }
-            else if (router.accepts(message.message_id))
+            else if (router.accepts(message.get_message_id()))
             {
               router.receive(source, message);
             }
@@ -245,7 +245,7 @@ namespace etl
           // Call all of them.
           while (range.first != range.second)
           {
-            if ((*(range.first))->accepts(message.message_id))
+            if ((*(range.first))->accepts(message.get_message_id()))
             {
               (*(range.first))->receive(source, message);
             }
@@ -253,7 +253,7 @@ namespace etl
             ++range.first;
           }
 
-          // Do any message busses.
+          // Do any message buses.
           // These are always at the end of the list.
           irouter = std::lower_bound(router_list.begin(),
                                      router_list.end(),
@@ -306,12 +306,12 @@ namespace etl
     //*******************************************
     struct compare_router_id
     {
-      bool operator()(etl::imessage_router* prouter, etl::message_router_id_t id) const
+      bool operator()(const etl::imessage_router* prouter, etl::message_router_id_t id) const
       {
         return prouter->get_message_router_id() < id;
       }
 
-      bool operator()(etl::message_router_id_t id, etl::imessage_router* prouter) const
+      bool operator()(etl::message_router_id_t id, const etl::imessage_router* prouter) const
       {
         return id < prouter->get_message_router_id();
       }
diff --git a/src/message_router.h b/src/message_router.h
index 23bcd119..5c33cd0d 100644
--- a/src/message_router.h
+++ b/src/message_router.h
@@ -104,7 +104,7 @@ namespace etl
     //********************************************
     bool accepts(const etl::imessage& msg) const
     {
-      return accepts(msg.message_id);
+      return accepts(msg.get_message_id());
     }
 
     //********************************************
@@ -214,7 +214,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -295,7 +295,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const etl::message_id_t id = msg.message_id;
+      const etl::message_id_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -356,7 +356,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -436,7 +436,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -496,7 +496,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -575,7 +575,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -634,7 +634,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -712,7 +712,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -769,7 +769,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -846,7 +846,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -902,7 +902,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -978,7 +978,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1033,7 +1033,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1108,7 +1108,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1162,7 +1162,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1236,7 +1236,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1288,7 +1288,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1361,7 +1361,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1412,7 +1412,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1484,7 +1484,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1533,7 +1533,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1604,7 +1604,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1652,7 +1652,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1722,7 +1722,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1768,7 +1768,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1837,7 +1837,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1882,7 +1882,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -1950,7 +1950,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -1994,7 +1994,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -2061,7 +2061,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
@@ -2104,7 +2104,7 @@ namespace etl
       //********************************************
       explicit message_packet(const etl::imessage& msg)
       {
-        const size_t id = msg.message_id;
+        const size_t id = msg.get_message_id();
 
         void* p = data;
 
@@ -2170,7 +2170,7 @@ namespace etl
     //**********************************************
     void receive(etl::imessage_router& source, const etl::imessage& msg)
     {
-      const size_t id = msg.message_id;
+      const size_t id = msg.get_message_id();
 
       switch (id)
       {
diff --git a/src/message_router_generator.h b/src/message_router_generator.h
index 7551b775..93b2680a 100644
--- a/src/message_router_generator.h
+++ b/src/message_router_generator.h
@@ -116,7 +116,7 @@ namespace etl
     //********************************************
     bool accepts(const etl::imessage& msg) const
     {
-      return accepts(msg.message_id);
+      return accepts(msg.get_message_id());
     }
 
     //********************************************
@@ -236,7 +236,7 @@ namespace etl
       cog.outl("    //********************************************")
       cog.outl("    explicit message_packet(const etl::imessage& msg)")
       cog.outl("    {")
-      cog.outl("      const size_t id = msg.message_id;")
+      cog.outl("      const size_t id = msg.get_message_id();")
       cog.outl("")
       cog.outl("      void* p = data;")
       cog.outl("")
@@ -315,7 +315,7 @@ namespace etl
       cog.outl("  //**********************************************")
       cog.outl("  void receive(etl::imessage_router& source, const etl::imessage& msg)")
       cog.outl("  {")
-      cog.outl("    const etl::message_id_t id = msg.message_id;")
+      cog.outl("    const etl::message_id_t id = msg.get_message_id();")
       cog.outl("")
       cog.outl("    switch (id)")
       cog.outl("    {")
@@ -392,7 +392,7 @@ namespace etl
           cog.outl("    //********************************************")
           cog.outl("    explicit message_packet(const etl::imessage& msg)")
           cog.outl("    {")
-          cog.outl("      const size_t id = msg.message_id;")
+          cog.outl("      const size_t id = msg.get_message_id();")
           cog.outl("")
           cog.outl("      void* p = data;")
           cog.outl("")
@@ -471,7 +471,7 @@ namespace etl
           cog.outl("  //**********************************************")
           cog.outl("  void receive(etl::imessage_router& source, const etl::imessage& msg)")
           cog.outl("  {")
-          cog.outl("    const size_t id = msg.message_id;")
+          cog.outl("    const size_t id = msg.get_message_id();")
           cog.outl("")
           cog.outl("    switch (id)")
           cog.outl("    {")
diff --git a/test/codeblocks/ETL.depend b/test/codeblocks/ETL.depend
index cc771703..1efb0a93 100644
--- a/test/codeblocks/ETL.depend
+++ b/test/codeblocks/ETL.depend
@@ -8248,14 +8248,14 @@
 	"map.h"
 	<algorithm>
 
-1501074198 source:d:\users\john\documents\programming\github\etl\test\test_fsm.cpp
+1501519465 source:d:\users\john\documents\programming\github\etl\test\test_fsm.cpp
 	"UnitTest++.h"
 	"fsm.h"
 	"enum_type.h"
 	"container.h"
 	<iostream>
 
-1501414024 d:\users\john\documents\programming\github\etl\src\fsm.h
+1501527698 d:\users\john\documents\programming\github\etl\src\fsm.h
 	<stdint.h>
 	"array.h"
 	"nullptr.h"
@@ -8268,7 +8268,7 @@
 
 1501263136 d:\users\john\documents\programming\github\etl\src\user_type.h
 
-1501419761 d:\users\john\documents\programming\github\etl\src\message_router.h
+1501527644 d:\users\john\documents\programming\github\etl\src\message_router.h
 	<stdint.h>
 	"message.h"
 	"message_types.h"
@@ -8277,7 +8277,7 @@
 	"exception.h"
 	"largest.h"
 
-1501074054 source:d:\users\john\documents\programming\github\etl\test\test_message_router.cpp
+1501527721 source:d:\users\john\documents\programming\github\etl\test\test_message_router.cpp
 	"UnitTest++.h"
 	"ExtraCheckMacros.h"
 	"message_router.h"
@@ -8322,7 +8322,7 @@
 	"type_traits.h"
 	"function.h"
 
-1501271821 d:\users\john\documents\programming\github\etl\src\message.h
+1501527784 d:\users\john\documents\programming\github\etl\src\message.h
 	<stdint.h>
 	"error_handler.h"
 	"exception.h"
@@ -8331,7 +8331,7 @@
 1501263347 d:\users\john\documents\programming\github\etl\src\message_types.h
 	<stdint.h>
 
-1501419244 source:d:\users\john\documents\programming\github\etl\test\test_message_bus.cpp
+1501491785 source:d:\users\john\documents\programming\github\etl\test\test_message_bus.cpp
 	"UnitTest++.h"
 	"ExtraCheckMacros.h"
 	"message_router.h"
@@ -8340,7 +8340,7 @@
 	"largest.h"
 	"packet.h"
 
-1501419692 d:\users\john\documents\programming\github\etl\src\message_bus.h
+1501527665 d:\users\john\documents\programming\github\etl\src\message_bus.h
 	<stdint.h>
 	<algorithm>
 	"algorithm.h"
diff --git a/test/test_message_router.cpp b/test/test_message_router.cpp
index 4af52cb3..c2890fb0 100644
--- a/test/test_message_router.cpp
+++ b/test/test_message_router.cpp
@@ -335,19 +335,19 @@ namespace
       Router2 r2;
 
       CHECK(r2.accepts(message1));
-      CHECK(r2.accepts(message1.message_id));
+      CHECK(r2.accepts(message1.get_message_id()));
 
       CHECK(r2.accepts(message2));
-      CHECK(r2.accepts(message2.message_id));
+      CHECK(r2.accepts(message2.get_message_id()));
 
       CHECK(!r2.accepts(message3));
-      CHECK(!r2.accepts(message3.message_id));
+      CHECK(!r2.accepts(message3.get_message_id()));
 
       CHECK(r2.accepts(message4));
-      CHECK(r2.accepts(message4.message_id));
+      CHECK(r2.accepts(message4.get_message_id()));
 
       CHECK(r2.accepts(message5));
-      CHECK(r2.accepts(message5.message_id));
+      CHECK(r2.accepts(message5.get_message_id()));
     }
 
     //=========================================================================