Exception with Foreign Key in MVC project - sql-server

Question

I'm trying to record a new entry on a table (HistoryRequestResponse), which one of the values is a foreign key to another table (HistoryRequests). I know for sure that the foreign key value (lets say 1090) exists on HistoryRequests, but when i permorm the db.SaveChanges() I get the following error:
The INSERT statement conflicted with the FOREIGN KEY constraint
"FK__HistoryRe__idReq__04AFB25B". The conflict occurred in database
"iDesk", table "dbo.HistoryRequests", column 'id'. The statement has
been terminated.
public partial class HistoryRequestResponse
{
public int id { get; set; }
public int idReq { get; set; }
public string submitUser { get; set; }
public string respType { get; set; }
public string description { get; set; }
public System.DateTime submitDate { get; set; }
public virtual ResponseType ResponseType { get; set; }
public virtual HistoryRequests HistoryRequests { get; set; }
}
public partial class HistoryRequests
{
public HistoryRequests()
{
this.HistoryRequestResponse = new HashSet<HistoryRequestResponse>();
}
public int id { get; set; }
public System.DateTime submitDate { get; set; }
public string title { get; set; }
public string description { get; set; }
public Nullable<System.DateTime> closeDate { get; set; }
public string priority { get; set; }
public string submitUser { get; set; }
public string responsible { get; set; }
public Nullable<int> serialNumber { get; set; }
public Nullable<int> area { get; set; }
public virtual Area Area1 { get; set; }
public virtual Computers Computers { get; set; }
public virtual ICollection<HistoryRequestResponse> HistoryRequestResponse { get; set; }
public virtual Priorities Priorities { get; set; }
}
Then I do the following in the POST method:
[HttpPost]
public ActionResult Reopen(int? id, string resp)
{
HistoryRequests request = db.HistoryRequests.Find(id);
try
{
var response = new HistoryRequestResponse()
{
respType = "Reabrir",
//HistoryRequests = request,
id = 0,
submitDate = DateTime.Now,
submitUser = User.Identity.Name,
description = resp
};
response.idReq = (int)id;
request.closeDate = null;
request.responsible = User.Identity.Name;
if (ModelState.IsValid)
{
db.HistoryRequestResponse.Add(response);
db.SaveChanges(); //WHERE I GET THE EXCEPTION
db.Entry(request).State = EntityState.Modified;
db.SaveChanges();
var email = from u in db.Users
where u.UserName.Equals(request.submitUser)
select u.Email;
//SmtpServer.SendEmail(email.SingleOrDefault(), requests.title, desc);
}
return RedirectToAction("Dashboard", "BHome");
}
catch (Exception e)
{
return Content("Erro ao reabrir o pedido");
}
}