diff --git a/Yavsc/Models/Billing/NominatvieCommand.cs b/Yavsc/Models/Billing/NominatvieCommand.cs
index 1f713c4e..a2dc1709 100644
--- a/Yavsc/Models/Billing/NominatvieCommand.cs
+++ b/Yavsc/Models/Billing/NominatvieCommand.cs
@@ -8,7 +8,8 @@ using Yavsc.Models.Workflow;
 namespace Yavsc.Models.Billing
 {
 
- public class NominativeServiceCommand : Query<Service> {
+ public class NominativeServiceCommand<T> : Query<T> where T:Service
+  {
 
     public string ClientId { get; set; }
 
diff --git a/Yavsc/Models/Booking/BookQuery.cs b/Yavsc/Models/Booking/BookQuery.cs
index aa261e3d..3309d9a5 100644
--- a/Yavsc/Models/Booking/BookQuery.cs
+++ b/Yavsc/Models/Booking/BookQuery.cs
@@ -10,7 +10,7 @@ namespace Yavsc.Models.Booking
     /// Query, for a date, with a given perfomer, at this given place.
     /// </summary>
 
-    public class BookQuery : NominativeServiceCommand {
+    public class BookQuery : NominativeServiceCommand<RendezVous> {
     /// <summary>
     /// The command identifier
     /// </summary>