diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index d9dd910fe0..46d1787dc1 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -333,7 +333,7 @@ class Order(LoggedModel):
 
         return self._is_still_available()
 
-    def _is_still_available(self, now_dt: datetime=None) -> Union[bool, str]:
+    def _is_still_available(self, now_dt: datetime=None, count_waitinglist=True) -> Union[bool, str]:
         error_messages = {
             'unavailable': _('The ordered product "{item}" is no longer available.'),
         }
@@ -351,7 +351,7 @@ class Order(LoggedModel):
                 for quota in quotas:
                     if quota.id not in quota_cache:
                         quota_cache[quota.id] = quota
-                        quota.cached_availability = quota.availability(now_dt)[1]
+                        quota.cached_availability = quota.availability(now_dt, count_waitinglist=count_waitinglist)[1]
                     else:
                         # Use cached version
                         quota = quota_cache[quota.id]
diff --git a/src/pretix/control/views/orders.py b/src/pretix/control/views/orders.py
index ffb9f1a750..e1021e28c6 100644
--- a/src/pretix/control/views/orders.py
+++ b/src/pretix/control/views/orders.py
@@ -469,7 +469,7 @@ class OrderExtend(OrderView):
             else:
                 try:
                     with self.order.event.lock() as now_dt:
-                        is_available = self.order._is_still_available(now_dt)
+                        is_available = self.order._is_still_available(now_dt, count_waitinglist=False)
                         if is_available is True:
                             self.form.save()
                             self.order.status = Order.STATUS_PENDING
diff --git a/src/tests/control/test_orders.py b/src/tests/control/test_orders.py
index 52bd89d58c..8430976224 100644
--- a/src/tests/control/test_orders.py
+++ b/src/tests/control/test_orders.py
@@ -360,6 +360,27 @@ def test_order_extend_overdue_quota_empty(client, env):
     assert o.expires.strftime("%Y-%m-%d %H:%M:%S") == newdate[:10] + " 23:59:59"
 
 
+@pytest.mark.django_db
+def test_order_extend_overdue_quota_blocked_by_waiting_list(client, env):
+    o = Order.objects.get(id=env[2].id)
+    o.status = Order.STATUS_EXPIRED
+    o.expires = now() - timedelta(days=5)
+    o.save()
+    q = Quota.objects.create(event=env[0], size=1)
+    q.items.add(env[3])
+    env[0].waitinglistentries.create(item=env[3], email='foo@bar.com')
+
+    newdate = (now() + timedelta(days=20)).strftime("%Y-%m-%d %H:%M:%S")
+    client.login(email='dummy@dummy.dummy', password='dummy')
+    response = client.post('/control/event/dummy/dummy/orders/FOO/extend', {
+        'expires': newdate
+    }, follow=True)
+    assert 'alert-success' in response.rendered_content
+    o = Order.objects.get(id=env[2].id)
+    assert o.expires.strftime("%Y-%m-%d %H:%M:%S") == newdate[:10] + " 23:59:59"
+    assert o.status == Order.STATUS_PENDING
+
+
 @pytest.mark.django_db
 def test_order_extend_expired_quota_left(client, env):
     o = Order.objects.get(id=env[2].id)