diff --git a/app/models/spree/calculator/sysmocom_value_calculator.rb b/app/models/spree/calculator/sysmocom_value_calculator.rb
index 596ac5c..bc54fb8 100644
--- a/app/models/spree/calculator/sysmocom_value_calculator.rb
+++ b/app/models/spree/calculator/sysmocom_value_calculator.rb
@@ -153,18 +153,26 @@ ZONE3 = {
         item_total
     end
 
-    def compute(order)
+    def extract_iso_code(o)
+        if o.kind_of?(Spree::Shipment)
+            return o.address.country.iso
+        end
+        return o.ship_address.country.iso
+    end
+
+    def compute(object)
         # This could be more than an order but not right now
-        shipping_value = total_value_no_tax(order)
+        shipping_value = total_value_no_tax(object)
+        iso_code = extract_iso_code(object)
 
         # Go through the zones by name...
-        if order.ship_address.country.iso == 'DE'
+        if iso_code == 'DE'
             return price_germany(shipping_value)
-        elsif ZONE1.has_key?(order.ship_address.country.iso)
+        elsif ZONE1.has_key?(iso_code)
             return price_package_zone1(shipping_value)
-        elsif ZONE2.has_key?(order.ship_address.country.iso)
+        elsif ZONE2.has_key?(iso_code)
             return price_package_zone2(shipping_value)
-        elsif ZONE3.has_key?(order.ship_address.country.iso)
+        elsif ZONE3.has_key?(iso_code)
             return price_package_zone3(shipping_value)
         else
             return price_package_zone4(shipping_value)