doesn't get IPv6 address in dhclient.conf reject statement

inserted in dhclient.conf

reject 192.168.201.5, fe80::c225:6ff:fec5:5ce9;

tried different notations :: :0: , Brackets around, additional mask , but everytimes I get

/etc/dhcp/dhclient.conf line 21: expecting numeric value.
reject 192.168.201.5, fe80:
                        ^
/etc/dhcp/dhclient.conf line 21: expecting ip-address or ip-address/prefixlen
reject 192.168.201.5, fe80:0000:c225:6ff:fec5:5ce9;

--------------------------------------------------------------
reason is to get some adjustable load balancing between different dual stack Consumer Routers.
Every prefix is assigned dynamic, the static default route is assigned to the link local address and the client can't really decide which global interface source Ipv6 to use for the elected default route.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: isc-dhcp-client 4.3.3-5ubuntu12.1
ProcVersionSignature: Ubuntu 4.4.0-47.68-generic 4.4.24
Uname: Linux 4.4.0-47-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Sun Nov 20 08:35:09 2016
InstallationDate: Installed on 2016-11-19 (0 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: isc-dhcp
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.dhcp.dhclient.conf: 2016-11-20T08:20:21.852408