map<bigint,...> on select is losing array keys

[ghost]

CREATE TABLE test (id ascii PRIMARY KEY, test map<bigint,text>);

INSERT INTO test (id, test) VALUES ('Hello', {7: 'World'});
INSERT INTO test (id, test) VALUES ('Foo', {3: 'Bar', 4: 'Baz'});

cqlsh> SELECT * FROM test;

 id    | test
-------+----------------------
 Hello |         {7: 'World'}
   Foo | {3: 'Bar', 4: 'Baz'}

$pdo = new \PDO('cassandra:host=localhost;port=9160');
$pdo->exec('USE ...;');

$stmt = $pdo->prepare('SELECT * FROM test;');
$stmt->execute();

echo '<pre>';
print_r($stmt->fetchAll(\PDO::FETCH_ASSOC));
echo '</pre>';

Array(
    [0] => Array(
        [id] => Hello
        [test] => Array(
            [0] => World // must be: [7] => World
        )
    )
    [1] => Array(
        [id] => Foo
        [test] => Array(
            // [3] => Bar // is lost
            [0] => Baz // must be: [4] => Baz
        )
    )
)