Cannot change $primary_key

[Keberdle]

It cannot change $primary_key of entity.
After save is still in database original value.

$ended_uniq_customer_actions = \Db\ActionsToCustomersUniq::find('all', array(
'conditions' => array(
'customers_uniq_id = ?',
16728
)
));

$ended_uniq_customer_actions[0]->customers_uniq_id = 15892;
$ended_uniq_customer_actions[0]->save();

class ActionsToCustomersUniq extends ActiveRecord\Model {
static $table_name = 'crm_actions_to_customers_uniq';
static $primary_key = array('actions_id','customers_uniq_id');
}

CREATE TABLE IF NOT EXISTS crm_actions_to_customers_uniq (
actions_id int(11) NOT NULL DEFAULT '0',
updated_at datetime DEFAULT NULL,
created_at datetime DEFAULT NULL,
customers_uniq_id int(11) NOT NULL DEFAULT '0',
PRIMARY KEY (customers_uniq_id,actions_id)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
-----------------------------+ | actions_id | customers_uniq_id |
-----------------------------+ | 3 | 16728 |
-----------------------------+

mysql Ver 14.14 Distrib 5.5.53, for debian-linux-gnu (x86_64) using readline 6.3

Thank You in advance for help