diff --git a/src/pretix/base/models/event.py b/src/pretix/base/models/event.py
index 3620050e2..e3e9ed3dd 100644
--- a/src/pretix/base/models/event.py
+++ b/src/pretix/base/models/event.py
@@ -1277,6 +1277,9 @@ class Event(EventMixin, LoggedModel):
         return not self.orders.exists() and not self.invoices.exists()
 
     def delete_sub_objects(self):
+        from .checkin import Checkin
+
+        Checkin.all.filter(successful=False, list__event=self).delete()
         self.cartposition_set.filter(addon_to__isnull=False).delete()
         self.cartposition_set.all().delete()
         self.vouchers.all().delete()