In native.c method: rb_object_id_generator_next, when time is NULL, we use rb_current_time_milliseconds() but this should be

if (argc == 0 || (argc == 1 && *time == Qnil)) {
  t = htonl(rb_current_time_in_milliseconds());  /* This line needs to be changed. */
else {
  t = htonl(NUM2UINT(rb_funcall(*time, rb_intern("to_i"), 0)));
}

When time is passed, its correctly doing a htonl(). Making this change, ensures that object_ids will be generated in ascending order.