diff --git a/src/backend/concrete_simulation.hh b/src/backend/concrete_simulation.hh
index e2da995..03b0237 100644
--- a/src/backend/concrete_simulation.hh
+++ b/src/backend/concrete_simulation.hh
@@ -73,8 +73,6 @@ namespace sgpem
      */
     void  stop();
 
-		bool step() throw(UserInterruptException, NullPolicyException, MalformedPolicyException);
-
     /**
       \brief This methods allows to change the way the simulation progresses.
 
diff --git a/src/holt_widget.hh b/src/holt_widget.hh
index 3b616bf..eb12512 100644
--- a/src/holt_widget.hh
+++ b/src/holt_widget.hh
@@ -21,11 +21,11 @@
 #ifndef HOLT_WIDGET_HH
 #define HOLT_WIDGET_HH 1
 
-
-
 #include "cairo_widget.hh"
+
 #include <sgpemv2/history_observer.hh>
 #include <sgpemv2/request.hh>
+#include <sgpemv2/sub_request.hh>
 #include <sgpemv2/simulation_observer.hh>
 
 #include <complex>