diff --git a/tryton-scripts/mailings.py b/tryton-scripts/mailings.py
index 2037523..6f85a40 100644
--- a/tryton-scripts/mailings.py
+++ b/tryton-scripts/mailings.py
@@ -98,7 +98,7 @@ def fee_invoice(env: Env):
         msg["From"] = env.args.email_from
         msg["To"] = email_address
         msg["Date"] = env.args.email_date or datetime.datetime.now()
-        msg["Subject"] = f"Beitragsrechnung {year.year} ({invoice.number})"
+        msg["Subject"] = f"Beitragsrechnung {year.year} ({invoice.number})" if invoice.number else f"Vorläufige Beitragsrechnung {year.year}"
         msg["Message-Id"] = member['message_id']
         msg.set_content(template.render(**template_args))
         with (env.args.output_dir / member['message_id']).open("wb") as mailfile: