Phalcon\Loader with composer

call_user_func(function () {
    $composerLoader = require_once __DIR__ . '/vendor/autoload.php';
    $loader = new Phalcon\Loader();

    $loader->registerNamespaces($composerLoader->getPrefixesPsr4(), true);
    $loader->registerNamespaces($composerLoader->getPrefixes(), true);
    $loader->registerClasses($composerLoader->getClassMap(), true);
    $loader->register();
    var_dump($composerLoader->getPrefixesPsr4());
    $loader->autoLoad('WeChat\\Utils');
});

when i execute php _loader.php the output is

array(10) {
  ["WeChat\"]=>
  array(1) {
    [0]=>
    string(39) "/Users/ian/Documents/prolove/src/WeChat"
  }
  ["Symfony\Component\Yaml\"]=>
  array(1) {
    [0]=>
    string(48) "/Users/ian/Documents/prolove/vendor/symfony/yaml"
  }
  ["React\Promise\"]=>
  array(1) {
    [0]=>
    string(53) "/Users/ian/Documents/prolove/vendor/react/promise/src"
  }
  ["Predis\"]=>
  array(1) {
    [0]=>
    string(53) "/Users/ian/Documents/prolove/vendor/predis/predis/src"
  }
  ["Phalcon\"]=>
  array(1) {
    [0]=>
    string(69) "/Users/ian/Documents/prolove/vendor/phalcon/incubator/Library/Phalcon"
  }
  ["GuzzleHttp\Stream\"]=>
  array(1) {
    [0]=>
    string(58) "/Users/ian/Documents/prolove/vendor/guzzlehttp/streams/src"
  }
  ["GuzzleHttp\Ring\"]=>
  array(1) {
    [0]=>
    string(58) "/Users/ian/Documents/prolove/vendor/guzzlehttp/ringphp/src"
  }
  ["Elasticsearch\"]=>
  array(1) {
    [0]=>
    string(81) "/Users/ian/Documents/prolove/vendor/elasticsearch/elasticsearch/src/Elasticsearch"
  }
  ["Doctrine\Instantiator\"]=>
  array(1) {
    [0]=>
    string(83) "/Users/ian/Documents/prolove/vendor/doctrine/instantiator/src/Doctrine/Instantiator"
  }
  ["App\"]=>
  array(1) {
    [0]=>
    string(36) "/Users/ian/Documents/prolove/src/App"
  }
}

Notice: Array to string conversion in /Users/ian/Documents/prolove/_loader.php on line 16

and I found the $loader->registerNamespace accept only

array(
  'namespace'=>'path'
)

not the composer's

array(
  'namespace'=>array('path1', 'path2')
)

Is this a problem?