Index: django-oscar-3.1/src/oscar/apps/basket/middleware.py
===================================================================
--- django-oscar-3.1.orig/src/oscar/apps/basket/middleware.py
+++ django-oscar-3.1/src/oscar/apps/basket/middleware.py
@@ -163,8 +163,8 @@ class BasketMiddleware:
             basket = cookie_basket
         else:
             # Anonymous user with no basket - instantiate a new basket
-            # instance.  No need to save yet.
-            basket = Basket()
+            # instance.
+            basket = Basket.objects.create(status=Basket.OPEN)
 
         # Cache basket instance for the during of this request
         request._basket_cache = basket
Index: django-oscar-3.1/src/oscar/apps/catalogue/product_attributes.py
===================================================================
--- django-oscar-3.1.orig/src/oscar/apps/catalogue/product_attributes.py
+++ django-oscar-3.1/src/oscar/apps/catalogue/product_attributes.py
@@ -20,7 +20,8 @@ class ProductAttributesContainer:
 
     def __init__(self, product):
         self.product = product
-        self.refresh()
+        if self.product.pk:
+            self.refresh()
 
     def refresh(self):
         values = self.get_values().select_related('attribute')
Index: django-oscar-3.1/src/oscar/apps/catalogue/abstract_models.py
===================================================================
--- django-oscar-3.1.orig/src/oscar/apps/catalogue/abstract_models.py
+++ django-oscar-3.1/src/oscar/apps/catalogue/abstract_models.py
@@ -598,7 +598,7 @@ class AbstractProduct(models.Model):
         """
         Test if this product has any stockrecords
         """
-        return self.stockrecords.exists()
+        return self.pk and self.stockrecords.exists()
 
     @property
     def num_stockrecords(self):
Index: django-oscar-3.1/tests/integration/shipping/test_scales.py
===================================================================
--- django-oscar-3.1.orig/tests/integration/shipping/test_scales.py
+++ django-oscar-3.1/tests/integration/shipping/test_scales.py
@@ -27,6 +27,7 @@ class TestScales(TestCase):
 
     def test_returns_zero_for_empty_basket(self):
         basket = Basket()
+        basket.save()
 
         scale = Scale(attribute_code='weight')
         self.assertEqual(0, scale.weigh_basket(basket))
Index: django-oscar-3.1/tests/integration/basket/test_models.py
===================================================================
--- django-oscar-3.1.orig/tests/integration/basket/test_models.py
+++ django-oscar-3.1/tests/integration/basket/test_models.py
@@ -15,6 +15,7 @@ class TestANewBasket(TestCase):
 
     def setUp(self):
         self.basket = Basket()
+        self.basket.save()
         self.basket.strategy = strategy.Default()
 
     def test_has_zero_lines(self):
Index: django-oscar-3.1/tests/integration/shipping/test_method.py
===================================================================
--- django-oscar-3.1.orig/tests/integration/shipping/test_method.py
+++ django-oscar-3.1/tests/integration/shipping/test_method.py
@@ -12,6 +12,7 @@ class TestFreeShipppingForEmptyBasket(Te
     def setUp(self):
         self.method = methods.Free()
         self.basket = Basket()
+        self.basket.save()
         self.charge = self.method.calculate(self.basket)
 
     def test_is_free(self):
@@ -43,6 +44,7 @@ class TestNoShippingRequired(TestCase):
     def setUp(self):
         self.method = methods.NoShippingRequired()
         basket = Basket()
+        basket.save()
         self.charge = self.method.calculate(basket)
 
     def test_is_free_for_empty_basket(self):
@@ -59,6 +61,7 @@ class TestFixedPriceShippingWithoutTax(T
     def setUp(self):
         self.method = methods.FixedPrice(D('10.00'))
         basket = Basket()
+        basket.save()
         self.charge = self.method.calculate(basket)
 
     def test_has_correct_charge(self):
@@ -75,6 +78,7 @@ class TestFixedPriceShippingWithTax(Test
             charge_excl_tax=D('10.00'),
             charge_incl_tax=D('12.00'))
         basket = Basket()
+        basket.save()
         self.charge = self.method.calculate(basket)
 
     def test_has_correct_charge(self):
Index: django-oscar-3.1/src/oscar/apps/customer/apps.py
===================================================================
--- django-oscar-3.1.orig/src/oscar/apps/customer/apps.py
+++ django-oscar-3.1/src/oscar/apps/customer/apps.py
@@ -11,6 +11,7 @@ class CustomerConfig(OscarConfig):
     label = 'customer'
     name = 'oscar.apps.customer'
     verbose_name = _('Customer')
+    default = True
 
     namespace = 'customer'
 
Index: django-oscar-3.1/tests/integration/shipping/test_discount.py
===================================================================
--- django-oscar-3.1.orig/tests/integration/shipping/test_discount.py
+++ django-oscar-3.1/tests/integration/shipping/test_discount.py
@@ -25,16 +25,19 @@ class TestDiscountingMethodsWithoutTax(T
 
     def test_delegates_is_tax_known(self):
         basket = Basket()
+        basket.save()
         charge = self.method.calculate(basket)
         self.assertFalse(charge.is_tax_known)
 
     def test_discounts_charge(self):
         basket = Basket()
+        basket.save()
         charge = self.method.calculate(basket)
         self.assertEqual(D('8.00'), charge.excl_tax)
 
     def test_can_have_tax_set_later(self):
         basket = Basket()
+        basket.save()
         charge = self.method.calculate(basket)
         charge.tax = D('1.00')
         self.assertEqual(D('9.00'), charge.incl_tax)
@@ -58,10 +61,12 @@ class TestDiscountingMethodsWithTax(Test
 
     def test_delegates_is_tax_known(self):
         basket = Basket()
+        basket.save()
         charge = self.method.calculate(basket)
         self.assertTrue(charge.is_tax_known)
 
     def test_discounts_charge(self):
         basket = Basket()
+        basket.save()
         charge = self.method.calculate(basket)
         self.assertEqual(D('7.00'), charge.incl_tax)