BIRD 3.3.1 persist option (proto kernel) not working

[artem]

After upgrade 3.2.2 -> 3.3.1 the ability to leave routes is broken.
When stop Bird, all routes are removed from the linux kernel.
Conf sample:

protocol static {
 ipv4;
 route 172.16.0.0/12 blackhole;
}
protocol kernel {
 persist;
 scan time 5;
 learn off;
 ipv4 {
  import none;
  export all;
 };
}