diff --git a/matlab/backward/checkdatabase.m b/matlab/backward/checkdatabase.m
index ac6d2f535..6c4dfa05a 100644
--- a/matlab/backward/checkdatabase.m
+++ b/matlab/backward/checkdatabase.m
@@ -23,14 +23,16 @@ function [dbase, info] = checkdatabase(dbase, DynareModel, inversionflag, simula
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
+% if DynareModel.maximum_endo_lead
+%    error('The model (%s) is assumed to be backward!', DynareModel.fname)
+% end
+
 if nargin<3
     inversionflag = false;
 end
 
-set_auxiliary_series = [DynareModel.fname '.dynamic_set_auxiliary_series'];
-
-if exist(['+' DynareModel.fname filesep() 'dynamic_set_auxiliary_series'])
-    dbase = feval(set_auxiliary_series, dbase, DynareModel.params);
+if exist(sprintf('+%s/dynamic_set_auxiliary_series', DynareModel.fname), 'file')
+    dbase = feval(sprintf('%s.dynamic_set_auxiliary_series', DynareModel.fname), dbase, DynareModel.params);
 end
 
 listoflaggedexogenousvariables = {};