diff --git a/src/storefront/cart.py b/src/storefront/cart.py
index d0e87c1..4f72b81 100644
--- a/src/storefront/cart.py
+++ b/src/storefront/cart.py
@@ -134,6 +134,10 @@ class Cart:
             }
 
     def deserialize(self, data):
+        # Transform old cart
+        if type(data) is list:
+            return
+
         try:
             self.coupon = Coupon.objects.get(code=data.get('coupon_code'))
         except Coupon.DoesNotExist: