diff --git a/sale.py b/sale.py
index 9e4278e..9481eb3 100644
--- a/sale.py
+++ b/sale.py
@@ -72,7 +72,7 @@ class Sale:
         shipment_zip = (self.shipment_address and self.shipment_address.zip
             or '')
         carrier = self.carrier
-        if not carrier.zips:
+        if not carrier or not carrier.zips:
             return res
         if (carrier and shipment_zip):
             for carrier_zip in carrier.zips: