diff --git a/froide_govplan/signals.py b/froide_govplan/signals.py
index 23f16fe..fb32d09 100644
--- a/froide_govplan/signals.py
+++ b/froide_govplan/signals.py
@@ -25,7 +25,7 @@ def send_mastodon_toot_update(sender, instance, created, **kwargs):
         transaction.on_commit(lambda: post_to_mastodon(
             f"📢 Neue Entwicklung im Verwaltungsvorhaben: {instance.plan.title}!\n\n"
             f"{instance.title}: {strip_html_tags(instance.content)}\n\n"
-            f"🔗 Primärquelle: {instance.reference}\n"
+            f"🔗 Primärquelle: {instance.url}\n"
             f"📋 Verwaltungstracker-Eintrag: {instance.plan.get_absolute_domain_url()}\n\n"
             f"#karlsruhe"
         ))