symfony: Expression engine doesn't handle expressions inside parameters

I’m getting _Call to undefined method Symfony\Component\ExpressionLanguage\Expression::_set_state() … in /app/var/cache/dev/appDevDebugProjectContainer.php line 8170

When I set up the parameter like:

parameters:
    session_save_path: "@=service('opensky.runtime_config').get('app.session_save_path')"

The line 8170 has the following code.

    protected function getDefaultParameters()
    {
        return array(
....
'session_save_path' => Symfony\Component\ExpressionLanguage\Expression::__set_state(array(
   'expression' => 'service(\'opensky.runtime_config\').get(\'app.session_save_path\')',
)),
....

The service that receives that specific parameter works just fine.