Can't disable ipv6

I have ipv6 disabled in the ipv6 tab, but my vpn interface tun0 still gets an ipv6 address after the vpn is established.

This used to work just fine in Xenial.

This makes so many things annoying to work with:
- google things I'm in the UK (where my vpn provider is)
- maps.google.com opens up in london instead of my home town
- browser defaults to ipv6 if a site has an ipv6 address, and all traffic goes through the much slower vpn instead of directly to the site
- if the vpn disconnects, which is a bit frequent with this provider, internet browsing fails for ipv6-enabled sites, even though my internet connection is just fine

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: network-manager-openvpn 1.2.10-0ubuntu2
ProcVersionSignature: Ubuntu 4.13.0-19.22-generic 4.13.13
Uname: Linux 4.13.0-19-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.7-0ubuntu3.6
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed Dec 13 14:47:29 2017
InstallationDate: Installed on 2017-09-24 (79 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170919)
SourcePackage: network-manager-openvpn
UpgradeStatus: No upgrade log present (probably fresh install)