xscreensaver user systemd unit is invalid

Apr 13 10:23:57 ottawa systemd[4959]: [/usr/lib/systemd/user/xscreensaver.service:5] Executable path is not absolute, ignoring: xscreensaver
Apr 13 10:23:57 ottawa systemd[4959]: xscreensaver.service: Service lacks both ExecStart= and ExecStop= setting. Refusing.
Apr 13 10:23:57 ottawa systemd[4959]: Reloading.

$ cat /usr/lib/systemd/user/xscreensaver.service
[Unit]
Description=XScreenSaver

[Service]
ExecStart=xscreensaver

[Install]
WantedBy=default.target

Instead the full path should be used in ExecStart, e.g.

/usr/bin/xscreensaver

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: xscreensaver 5.36-1ubuntu1
ProcVersionSignature: Ubuntu 4.10.0-19.21-generic 4.10.8
Uname: Linux 4.10.0-19-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.4-0ubuntu4
Architecture: amd64
CurrentDesktop: Unity:Unity7
Date: Thu Apr 13 10:27:22 2017
InstallationDate: Installed on 2016-01-26 (443 days ago)
InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Alpha amd64 (20160125)
SourcePackage: xscreensaver
UpgradeStatus: Upgraded to zesty on 2016-12-05 (128 days ago)