dhcp v6 4.3.1 impossible condition exit when fixed-prefix6 used

[Алексей Прокопчук]

Good time of the day!

My English is not very good, excuse me if I said something wrong.

I just upgrade my dhcp 4.2.5 to 4.3.1 and have dhcpd v6 fatal exit when use
'fixed-prefix6' parameter in host section. Server starts normally and
works fine
until my Mikrotik router tries to request IPv6 address. Then dhcpd exits
with
message in log file:

Jan 13 04:47:33 home-gw dhcpd: Impossible condition at dhcpv6.c:4304.

Without fixed-prefix6 parameter all works as usual.
I can't understand where I missed something?

Here is my very simple configuration which works fine with 4.2.5:

***********************************
option domain-name "test.local";
option dhcp6.name-servers 2a02:xxxx:8::1, 2a02:xxxx:8::5;
default-lease-time 3600;
max-lease-time 7200;
ddns-update-style none;
authoritative;

allow leasequery;

shared-network test
{

 subnet6 2a02:xxxx:8:1::/64
 {
  range6 2a02:xxxx:8:1::2 2a02:xxxx:8:1::6fff;
  prefix6 2a02:xxxx:8:101:: 2a02:xxxx:8:11f:: /64;

  host alexpro-book
  {
   hardware ethernet 3c:97:0e:2c:ee:4a;
   fixed-address6 2a02:xxxx:8:1::7700;
  }

  host alexpro-wife
  {
   hardware ethernet E0:CB:4E:40:9F:55;
   fixed-address6 2a02:xxxx:8:1::7711;
  }
 
   host alexpro-router
  {
   hardware ethernet D4:CA:6D:EE:14:C3;
   fixed-address6 2a02:xxxx:8:1::9999;
   ###The string below causes fatal exit
   fixed-prefix6 2a02:xxxx:8:100::/64;
  }
 
 }
**************************************

Thanks for attention, with best regards, Alexey Prokopchuk (AP8686-RIPE)