Problème comment et post_id

Bonjour,
Je suis en train de faire mes pages d'articles sur mon site web et j'ai cette erreur quand j'envoie mon commentaire :

Database Error
Error: SQLSTATE[HY000]: General error: 1364 Field 'post_id' doesn't have a default value

SQL Query: INSERT INTO `sitefin`.`comments` (`username`, `mail`, `content`, `created`) VALUES ('fffffffffffff', 'fffffffffffffff@ffffffff.com', 'efuihzefuihzreuilefzghoqil', '2016-06-22 18:46:36')

Notice: If you want to customize this error message, create app\View\Errors\pdo_error.ctp

Stack Trace
CORE\Cake\Model\Datasource\DboSource.php line 461 → PDOStatement->execute(array)
CORE\Cake\Model\Datasource\DboSource.php line 427 → DboSource->_execute(string, array)
CORE\Cake\Model\Datasource\DboSource.php line 1014 → DboSource->execute(string)
CORE\Cake\Model\Model.php line 1928 → DboSource->create(Comment, array, array)
CORE\Cake\Model\Model.php line 1751 → Model->_doSave(null, array)
APP\Controller\PostsController.php line 69 → Model->save(null, boolean, array)
[internal function] → PostsController->show(string, string)
CORE\Cake\Controller\Controller.php line 490 → ReflectionMethod->invokeArgs(PostsController, array)
CORE\Cake\Routing\Dispatcher.php line 193 → Controller->invokeAction(CakeRequest)
CORE\Cake\Routing\Dispatcher.php line 167 → Dispatcher->_invoke(PostsController, CakeRequest)
APP\webroot\index.php line 57 → Dispatcher->dispatch(CakeRequest, CakeResponse)

Voici le code concerné :

function show($id = null,$slug = null){
        if(!$id)
            throw new NotFoundException('Aucunes pages ne correspond à cet ID');
        $post = $this->Post->find('first',array(
            'conditions' => array('Post.id' => $id),
            'recursive' => 0
            ));
        if(empty($post))
            throw new NotFoundException('Aucunes pages ne correspond à cet ID');

        if($slug != $post['Post']['slug'])
            $this->redirect($post['Post']['link'],301);
        $d['post'] = $post;
        $this->set($d);
        // Comment submission
        if(!empty($this->request->data)){
            $this->Post->Comment->create($this->request->data, true);
            $this->request->data['Comment']['post_id'] = $post['Post']['id'];
            if($this->Post->Comment->save(null, true, array('mail', 'username', 'content', 'post_id'))){
                $this->Session->setFlash("Thanks for your comment","success");
                return $this->redirect($this->referer());
            }else{
                $this->Session->setFlash("You have to correct your errors first","error");
            }
        }
    }

Merci d'avance !