Standalone PDO instance gets connected but I get an auth error when passed to redbean

This is my simple PDO instance example:

try {
            $dbh = new PDO('mysql:host=my-db-server-instance;port=3306;dbname=MY_DB_NAME','admin','mypass');
            foreach($dbh->query('SELECT * from user limit 10') as $row) {
                print_r($row);
            }
            $dbh = null;
            die();
    } catch (PDOException $e) {
            print "Error!: " . $e->getMessage() . "<br/>";
            die();
    }

This works as intended. The problem is when I try to use redbean with this PDO instance (Using setup method to pass params doesn’t work either):

$dbh = new PDO('mysql:host=my-db-server-instance;port=3306;dbname=MY_DB_NAME','admin','mypass');
R::setup($dbh);

This shows this auth error: code 500 — VERBOSE: Internal error: /srv/app/djf9839484/htdocs/service/vendor/gabordemooij/redbean/RedBeanPHP/Driver/RPDO.php line 206 : SQLSTATE[28000]: Invalid authorization specification: 1045 Access denied for user ‘admin’@’%’ (using password: YES)”

Have been checking sources and everything seems ok. Has anybody found a solution to this problem?