diff --git a/storefront/views.py b/storefront/views.py
index 03152dc..78f2797 100644
--- a/storefront/views.py
+++ b/storefront/views.py
@@ -115,7 +115,7 @@ class CartAddProductView(SingleObjectMixin, FormView):
             cleaned_data = form.cleaned_data
             cart.add_item(
                 CartItem({
-                    'variant_pk': cleaned_data.pop('variant'),
+                    'variant_pk': cleaned_data.pop('variant').pk,
                     'quantity': cleaned_data.pop('quantity'),
                     'options': cleaned_data
                 })