diff --git a/doc/manual/utils/dynare_dom.py b/doc/manual/utils/dynare_dom.py
index e5b54c1f709e4a9777eb03d863352048af52f7f1..101bb7345ec044b5156ce70b5d3a625f7cbcd397 100644
--- a/doc/manual/utils/dynare_dom.py
+++ b/doc/manual/utils/dynare_dom.py
@@ -97,7 +97,7 @@ class DynObject(ObjectDescription):
                 self.state_machine.reporter.warning(
                     'duplicate object description of %s, ' % fullname +
                     'other instance in ' +
-                    self.env.doc2path(objects[fullname][0]),line=self.lineno)
+                    str(self.env.doc2path(objects[fullname][0])),line=self.lineno)
             objects[fullname] = (self.env.docname, self.objtype)
 
         indextext = self.get_index_text(fullname,name_obj)