diff --git a/src/pretix/base/services/orders.py b/src/pretix/base/services/orders.py
index dd5947c4e..5d1d61153 100644
--- a/src/pretix/base/services/orders.py
+++ b/src/pretix/base/services/orders.py
@@ -2114,8 +2114,8 @@ class OrderChangeManager:
                             or (a.variation and not a.variation.all_sales_channels and not a.variation.limit_sales_channels.contains(self.order.sales_channel))
                             or a.item.unavailability_reason(has_voucher=True, subevent=a.subevent)
                             or (
-                                not item.all_sales_channels and
-                                not item.limit_sales_channels.contains(self.order.sales_channel)
+                                not a.item.all_sales_channels and
+                                not a.item.limit_sales_channels.contains(self.order.sales_channel)
                             )
                         )
                         if is_unavailable:
diff --git a/src/tests/presale/test_order_change.py b/src/tests/presale/test_order_change.py
index 0bcafeb4e..24c110c38 100644
--- a/src/tests/presale/test_order_change.py
+++ b/src/tests/presale/test_order_change.py
@@ -1015,7 +1015,8 @@ class OrderChangeAddonsTest(BaseOrdersTest):
             '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
         )
         assert response.status_code == 200
-        assert 'Workshop 1' not in response.content.decode()
+        assert '<li>1x Workshop 1</li>' in response.content.decode()
+        assert f'cp_{self.ticket_pos.pk}_item_{self.workshop1.pk}' not in response.content.decode()
 
         response = self.client.post(
             '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
@@ -1035,6 +1036,39 @@ class OrderChangeAddonsTest(BaseOrdersTest):
         with scopes_disabled():
             assert self.ticket_pos.addons.count() == 2
 
+    def test_do_not_overbook_unavailable_on_adding(self):
+        self.iao.max_count = 1
+        self.iao.save()
+        self.workshop1.available_until = now() - datetime.timedelta(days=1)
+        self.workshop1.save()
+        with scopes_disabled():
+            OrderPosition.objects.create(
+                order=self.order,
+                item=self.workshop1,
+                variation=None,
+                price=Decimal("12"),
+                addon_to=self.ticket_pos,
+                attendee_name_parts={'full_name': "Peter"}
+            )
+            self.order.total += Decimal("12")
+            self.order.save()
+
+        response = self.client.get(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret)
+        )
+        assert response.status_code == 200
+        assert '<li>1x Workshop 1</li>' in response.content.decode()
+        assert f'cp_{self.ticket_pos.pk}_item_{self.workshop1.pk}' not in response.content.decode()
+
+        response = self.client.post(
+            '/%s/%s/order/%s/%s/change' % (self.orga.slug, self.event.slug, self.order.code, self.order.secret),
+            {
+                f'cp_{self.ticket_pos.pk}_variation_{self.workshop2.pk}_{self.workshop2a.pk}': '1'
+            },
+            follow=True
+        )
+        assert 'alert-danger' in response.content.decode()
+
     def test_remove_addon_checked_in(self):
         with scopes_disabled():
             self.event.settings.change_allow_user_if_checked_in = True