--- a/Framework/Messages/MessageBroker.h	Wed May 29 13:44:55 2019 +0200
+++ b/Framework/Messages/MessageBroker.h	Wed May 29 16:15:04 2019 +0200
@@ -18,8 +18,9 @@
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  **/
 
+#pragma once
 
-#pragma once
+#include "../StoneException.h"
 
 #include "boost/noncopyable.hpp"
 
@@ -40,6 +41,13 @@
     std::set<const IObserver*> activeObservers_;  // the list of observers that are currently alive (that have not been deleted)
 
   public:
+    MessageBroker()
+    {
+      static bool created = false;
+      ORTHANC_ASSERT(!created, "One broker to rule them all!");
+      created = true;
+    }
+
     void Register(const IObserver& observer)
     {
       activeObservers_.insert(&observer);