diff --git a/doc/manual/utils/dynare_dom.py b/doc/manual/utils/dynare_dom.py
index 101bb7345ec044b5156ce70b5d3a625f7cbcd397..98233a4b4611faf9efd35055f073ba7e590a9ced 100644
--- a/doc/manual/utils/dynare_dom.py
+++ b/doc/manual/utils/dynare_dom.py
@@ -242,7 +242,7 @@ class DynSimpleObject(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)