@@ -1145,0 +1143,4 @@
+                    # first step,
+                    if not (get_session().user or get_session().anonymous_formdata_keys):
+                        # that means we probably lost the session in mid-air.
+                        get_session().message = ('error', _('Sorry, your session have been lost.'))

@@ -1381,7 +1386,13 @@ class FormPage(Directory, TempfileDirectoryMixin, FormTemplateMixin):
             if form.has_errors() or form.get_submit() is True:
                 if self.has_draft_support() and not honeypot_error:
                     # always save draft during server roundtrip, even if the form has errors