Greeter misaligned on multiple displays

The greeter is misaligned when started with multiple displays of different geometry. Dis- and re-connecting the external screen makes it go good again.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: unity8-greeter 8.14+16.04.20160914-0ubuntu1 [origin: LP-PPA-ci-train-ppa-service-landing-078]
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
NonfreeKernelModules: zfs zunicode zcommon znvpair zavl
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: Unity
Date: Wed Sep 14 12:22:09 2016
InstallationDate: Installed on 2016-05-06 (130 days ago)
InstallationMedia: Ubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1)
SourcePackage: unity8
UpgradeStatus: No upgrade log present (probably fresh install)