diff --git a/src/pretix/multidomain/middlewares.py b/src/pretix/multidomain/middlewares.py
index 416cbd7718..e2ce989712 100644
--- a/src/pretix/multidomain/middlewares.py
+++ b/src/pretix/multidomain/middlewares.py
@@ -40,14 +40,14 @@ class MultiDomainMiddleware(MiddlewareMixin):
             request.host = domain
             request.port = int(port) if port else None
 
-            orga = cache.get('pretix_multidomain_organizer_{}'.format(domain))
+            orga = cache.get('pretix_multidomain_organizer_instance_{}'.format(domain))
             if orga is None:
                 try:
                     kd = KnownDomain.objects.select_related('organizer').get(domainname=domain)  # noqa
                     orga = kd.organizer
                 except KnownDomain.DoesNotExist:
                     orga = False
-                cache.set('pretix_multidomain_organizer_{}'.format(domain), orga.pk if orga else False, 3600)
+                cache.set('pretix_multidomain_organizer_instance_{}'.format(domain), orga, 3600)
 
             if orga:
                 request.organizer_domain = True
diff --git a/src/pretix/multidomain/models.py b/src/pretix/multidomain/models.py
index 23606a2346..20247b6429 100644
--- a/src/pretix/multidomain/models.py
+++ b/src/pretix/multidomain/models.py
@@ -21,9 +21,11 @@ class KnownDomain(models.Model):
         if self.organizer:
             self.organizer.get_cache().clear()
         cache.delete('pretix_multidomain_organizer_{}'.format(self.domainname))
+        cache.delete('pretix_multidomain_organizer_instance_{}'.format(self.domainname))
 
     def delete(self, *args, **kwargs):
         if self.organizer:
             self.organizer.get_cache().clear()
         cache.delete('pretix_multidomain_organizer_{}'.format(self.domainname))
+        cache.delete('pretix_multidomain_organizer_instance_{}'.format(self.domainname))
         super().delete(*args, **kwargs)
diff --git a/src/tests/multidomain/test_urlreverse.py b/src/tests/multidomain/test_urlreverse.py
index 93e3f7348c..a8d65f1d99 100644
--- a/src/tests/multidomain/test_urlreverse.py
+++ b/src/tests/multidomain/test_urlreverse.py
@@ -99,7 +99,7 @@ def test_event_custom_domain_cache(env):
 })
 def test_event_custom_domain_cache_clear(env):
     kd = KnownDomain.objects.create(domainname='foobar', organizer=env[0])
-    env[0].get_cache().clear()
+    env[0].cache.clear()
     with assert_num_queries(1):
         eventreverse(env[1], 'presale:event.index')
     kd.delete()