diff --git a/CSharp/sample-payments/PaymentsBot/Controllers/MessagesController.cs b/CSharp/sample-payments/PaymentsBot/Controllers/MessagesController.cs
index 7a317d64b0..fa197f15d4 100644
--- a/CSharp/sample-payments/PaymentsBot/Controllers/MessagesController.cs
+++ b/CSharp/sample-payments/PaymentsBot/Controllers/MessagesController.cs
@@ -148,11 +148,10 @@ private async Task OnInvoke(IInvokeActivity invoke, IConnectorClient connectorCl
                 }
             }
 
-            // do not require or check default selected option
-            //if (result.Details.ShippingOptions.Count(option => option.Selected.HasValue && option.Selected.Value) != 1)
-            //{
-            //    throw new ArgumentException("Expected exactly zero or one selected shipping option.");
-            //}
+            if (result.Details.ShippingOptions.Count(option => option.Selected.HasValue && option.Selected.Value) > 1)
+            {
+                throw new ArgumentException("Expected exactly zero or one selected shipping option.");
+            }
 
             // update payment details after shipping changed
             await this.shippingService.UpdatePaymentDetailsAsync(result.Details, paymentRequestUpdate.ShippingAddress, catalogItem);