Multiple mails to CC and BCC

There is an issue when we send a email with CC or BCC to a third person. The mail arrives to the CC recipient but it does so as TO destinatary and CC destinatary.

The email arrives as this:
to: mainrecipient@civicrm.org, ccrecipient@civicrm.org
cc: ccrecipient@civicrm.org

and would have to be as:
to: mainrecipient@civicrm.org
cc: ccrecipient@civicrm.org

I check the code and I think that the error is on CRM/Utils/Mail.php file

line 169:
if (CRM_Utils_Array::value('Cc', $headers)) {
$to[] = CRM_Utils_Array::value('Cc', $headers);

line 181:
$result = $mailer->send($to, $headers, $message);