Cannot disable CI Session handling in v4.5.1

I had to comment out this block to make PHP sessions work correctly, as it worked well in previous CI versions :
/*

Code:

if (isset($_SESSION)) {
    session()->set('_ci_previous_url', URI::createURIString(
        $uri->getScheme(),
        $uri->getAuthority(),
        $uri->getPath(),
        $uri->getQuery(),
        $uri->getFragment()
    ));
}
*/

Using CI sessions shouldn't be mandatory. There should be a simple option to disable CI sessions and use native PHP sessions instead.