RTNETLINK answers: Operation not supported

[WeakTopology]

I'm not sure if I'm missing a package, but I can't get vpnshift to run.

$ /path/to/vpnshift -c mullvad.conf curl -s http://myip.dnsomatic.com
RTNETLINK answers: Operation not supported
failed: nsdo ip address add ::1/128 dev lo
openvpn exited
openvpn exited

In comparison, the following works fine:

$ sudo openvpn --config mullvad.conf

I also tried sudo vpnshift (I wasn't sure if it was necessary), but this failed as above.

My system is a Raspberry Pi running Raspbian. I'm happy to provide more details if useful.