diff --git a/src/tests/presale/test_cart.py b/src/tests/presale/test_cart.py
index 61c885d2be..2f59e7205d 100644
--- a/src/tests/presale/test_cart.py
+++ b/src/tests/presale/test_cart.py
@@ -200,6 +200,32 @@ class CartTest(CartTestMixin, TestCase):
         self.assertIn('numbers only', doc.select('.alert-danger')[0].text)
         self.assertFalse(CartPosition.objects.filter(cart_id=self.session_key, event=self.event).exists())
 
+        response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+            'item_%d' % self.ticket.id: '-2',
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+        doc = BeautifulSoup(response.rendered_content)
+        self.assertIn('numbers only', doc.select('.alert-danger')[0].text)
+        self.assertFalse(CartPosition.objects.filter(cart_id=self.session_key, event=self.event).exists())
+        response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+            'variation_%d_%d' % (self.shirt.id, self.shirt_blue.id): 'a',
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+        doc = BeautifulSoup(response.rendered_content)
+        self.assertIn('numbers only', doc.select('.alert-danger')[0].text)
+        self.assertFalse(CartPosition.objects.filter(cart_id=self.session_key, event=self.event).exists())
+
+        response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+            'variation_a_%d' % (self.shirt_blue.id): '-2',
+        }, follow=True)
+        self.assertRedirects(response, '/%s/%s/' % (self.orga.slug, self.event.slug),
+                             target_status_code=200)
+        doc = BeautifulSoup(response.rendered_content)
+        self.assertIn('numbers only', doc.select('.alert-danger')[0].text)
+        self.assertFalse(CartPosition.objects.filter(cart_id=self.session_key, event=self.event).exists())
+
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
         }, follow=True)
         self.assertRedirects(response, '/%s/%s/' % (self.orga.slug, self.event.slug),