[SalesForce] Variable does not exist error

I have this code:

@HttpPost   
global static String doPost() { 
    RestRequest req = RestContext.request;
    RestResponse res = RestContext.response;
    if(req.params.get('action') == 'create'){
        System.debug('json'+req.requestbody);
        evticket__c ticket = createTicket(req);
        return 'yes';
    }
    else{
        return 'no';
    }

}

public class TicketObject {
    String Subject;
    String Description;
    List<CommentObject> Comments = new List<CommentObject>();

    public TicketObject(String s, String d)
    {
        Subject = s;
        Description = d;

    }
}

public static evticket__c createTicket(RestRequest req){
    //req.requestBody.toString();

    System.debug(req.requestbody.tostring());
    TicketObject ticketObject = (TicketObject)JSON.deserialize(req.requestbody.tostring(), TicketObject.class);

    evticket__c newTicket = new evticket__c(Subject__c = ticketObject.Subject, Description__c = ticketObject.Description);
    //newTicket.Subject__c = 'test1';
    //newTicket.Description__c = 'test1';
    insert newTicket;
    return newTicket;
}

in this line of code:

TicketObject ticketObject = (TicketObject)JSON.deserialize(req.requestbody.tostring(), TicketObject.class);

i get this error:

Compilation error: Variable does not exist: TicketObject.class

Any ideas?