diff --git a/db/migrate/20181123012635_associate_customers_to_users.rb b/db/migrate/20181123012635_associate_customers_to_users.rb
new file mode 100644
index 0000000000..b42739ff68
--- /dev/null
+++ b/db/migrate/20181123012635_associate_customers_to_users.rb
@@ -0,0 +1,42 @@
+# When we introduced the Customer model, we didn't associate any existing
+# customers with users that have the same email address.
+# Later we decided to create that association when users sign up. But we didn't
+# update all the existing customers. We do that now for data consistency and to
+# solve several bugs.
+#
+# - https://github.com/openfoodfoundation/openfoodnetwork/pull/2084
+# - https://github.com/openfoodfoundation/openfoodnetwork/issues/2841
+class AssociateCustomersToUsers < ActiveRecord::Migration
+  class Customer < ActiveRecord::Base
+  end
+
+  def up
+    save_customers
+    execute "UPDATE customers
+              SET user_id = spree_users.id
+              FROM spree_users
+              WHERE customers.email = spree_users.email
+               AND customers.user_id IS NULL;"
+  end
+
+  def down
+    customers = backed_up_customers
+    Customer.where(id: customers).update_all(user_id: nil)
+  end
+
+  def save_customers
+    customers = Customer.
+      joins("INNER JOIN spree_users ON customers.email = spree_users.email").
+      where(user_id: nil).all
+
+    File.write(backup_file, Marshal.dump(customers))
+  end
+
+  def backed_up_customers
+    Marshal.load(File.read(backup_file))
+  end
+
+  def backup_file
+    File.join("log", "customers_without_user_association.log")
+  end
+end
diff --git a/spec/support/request/shop_workflow.rb b/spec/support/request/shop_workflow.rb
index 876f184644..9df7f72126 100644
--- a/spec/support/request/shop_workflow.rb
+++ b/spec/support/request/shop_workflow.rb
@@ -13,7 +13,7 @@ module ShopWorkflow
   end
 
   def set_order(order)
-    ApplicationController.any_instance.stub(:session).and_return({order_id: order.id, access_token: order.token})
+    allow_any_instance_of(ApplicationController).to receive(:session).and_return({order_id: order.id, access_token: order.token})
   end
 
   def add_product_to_cart(order, product, quantity: 1)