Asp .net hidden field can't set value with jquery

I can't set the value of a hidden field with jquery in asp .net.

My hidden field is declared like this:

<asp:HiddenField runat="server" ID="hdnSelectedTicket" />

And this is how I set the value:

            alert(ticketID);
            $('#<%=hdnSelectedTicket.ClientID %>').val(ticketID);
            alert($('#<%=hdnSelectedTicket.ClientID %>').val());

Both alerts show the right value but when I fetch it at the server it is empty.