diff --git a/lib/mws/fulfillment_inbound_shipment/client.rb b/lib/mws/fulfillment_inbound_shipment/client.rb
index <HASH>..<HASH> 100644
--- a/lib/mws/fulfillment_inbound_shipment/client.rb
+++ b/lib/mws/fulfillment_inbound_shipment/client.rb
@@ -362,6 +362,7 @@ module MWS
           .add('ShipmentId' => shipment_id,
                'InboundShipmentHeader' => inbound_shipment_header)
           .structure!('InboundShipmentItems', 'member')
+          .structure!('PrepDetailsList', 'member')
       end
     end
   end
prep_list support for build inbound shipment