igbinary segfault reproduce on php7

igbinary_reproduce.php

<?php

$result = [];

for ($i = 0; $i < 40; $i++) {
  $inner = new stdClass;
  $inner->a = $i % 25;
  $result[0][$inner->a][$i] = $inner;
  $result[1][] = $inner;
}

igbinary_unserialize(igbinary_serialize($result));

With 10 items it doesn't segfault

If replace

$result[1][] = $inner;

with

$result[1][] = clone $inner;

it does not segfault either