Mass assignment + custom setter which modifies value type

gistfile1.php

Class Task extends ActiveRecord\Model
{

 public static $table = 'tasks';

 public function set_history($history)
 {
  $this->assign_attribute('history', serialize($history));
 }

 public function get_history()
 {
  return unserialize($this->read_attribute('history'));
 }

}

$task = new Task(array('history' => array('created' => '12_20_2011')));
$task->history === array('created' => '12_20_2011'); // this should work, but it's false
$task->history === 'Array'; // unfortunately this is true due to model property casting done before custom setter