diff --git a/pyproject.toml b/pyproject.toml
index 20f977d1f..43cd6059e 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,7 +42,7 @@ dependencies = [
   "django-filter==25.1",
   "django-formset-js-improved==0.5.0.3",
   "django-formtools==2.5.1",
-  "django-hierarkey==1.2.*",
+  "django-hierarkey==2.0.*",
   "django-hijack==3.7.*",
   "django-i18nfield==1.10.*",
   "django-libsass==0.9",
diff --git a/src/pretix/base/migrations/0286_settingsstore_unique.py b/src/pretix/base/migrations/0286_settingsstore_unique.py
new file mode 100644
index 000000000..eb93adeac
--- /dev/null
+++ b/src/pretix/base/migrations/0286_settingsstore_unique.py
@@ -0,0 +1,28 @@
+# Generated by Django 4.2.16 on 2025-08-14 09:40
+
+from django.db import migrations
+from hierarkey.utils import CleanHierarkeyDuplicates
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("pretixbase", "0285_voucher_created"),
+    ]
+
+    operations = [
+        CleanHierarkeyDuplicates("GlobalSettingsObject_SettingsStore"),
+        CleanHierarkeyDuplicates("Organizer_SettingsStore"),
+        CleanHierarkeyDuplicates("Event_SettingsStore"),
+        migrations.AlterUniqueTogether(
+            name="event_settingsstore",
+            unique_together={("object", "key")},
+        ),
+        migrations.AlterUniqueTogether(
+            name="globalsettingsobject_settingsstore",
+            unique_together={("key",)},
+        ),
+        migrations.AlterUniqueTogether(
+            name="organizer_settingsstore",
+            unique_together={("object", "key")},
+        ),
+    ]
diff --git a/src/pretix/base/models/event.py b/src/pretix/base/models/event.py
index 7f28f2e97..c5b5061f8 100644
--- a/src/pretix/base/models/event.py
+++ b/src/pretix/base/models/event.py
@@ -1085,7 +1085,7 @@ class Event(EventMixin, LoggedModel):
             s.save(force_insert=True)
 
         valid_sales_channel_identifers = set(self.organizer.sales_channels.values_list("identifier", flat=True))
-        skip_settings = (
+        skip_settings = {
             'ticket_secrets_pretix_sig1_pubkey',
             'ticket_secrets_pretix_sig1_privkey',
             # no longer used, but we still don't need to copy them
@@ -1093,7 +1093,10 @@ class Event(EventMixin, LoggedModel):
             'presale_css_checksum',
             'presale_widget_css_file',
             'presale_widget_css_checksum',
-        )
+        } | {
+            # Some settings might already exist due to e.g. the timezone being special in the API
+            s.key for s in self.settings._objects.all()
+        }
         settings_to_save = []
         for s in other.settings._objects.all():
             if s.key in skip_settings: