diff --git a/tabellio/documents/dossier.py b/tabellio/documents/dossier.py
index ef3c2f6..899a145 100644
--- a/tabellio/documents/dossier.py
+++ b/tabellio/documents/dossier.py
@@ -195,7 +195,10 @@ class Dossier(Item, BasePublication):
 
     @property
     def reftitle(self):
-        return '%s - %s (%s)' % (self.dostype_str, self.no, self.session)
+        if self.no:
+            return '%s - %s (%s)' % (self.dostype_str, self.no, self.session)
+        else:
+            return '%s (%s)' % (self.dostype_str, self.session)
 
     @property
     def associated_docs(self):