"systemctl enable mdmonitor" fails

mdadm package appears to not be complete.

trying to enable mdmonitor to launch automatically for systemd, but it fails with this warning:

# systemctl enable mdmonitor
The unit files have no installation config (WantedBy, RequiredBy, Also, Alias
settings in the [Install] section, and DefaultInstance for template units).
This means they are not meant to be enabled using systemctl.
Possible reasons for having this kind of units are:
1) A unit may be statically enabled by being symlinked from another unit's
   .wants/ or .requires/ directory.
2) A unit's purpose may be to act as a helper for some other unit which has
   a requirement dependency on it.
3) A unit may be started when needed via activation (socket, path, timer,
   D-Bus, udev, scripted systemctl call, ...).
4) In case of template units, the unit is meant to be enabled with some
   instance name specified.

I am able to start mdmonitor.

# systemctl status mdmonitor
● mdmonitor.service - MD array monitor
   Loaded: loaded (/lib/systemd/system/mdmonitor.service; static; vendor preset: enabled)
   Active: active (running) since Thu 2018-01-04 12:47:01 EST; 30min ago
 Main PID: 3052 (mdadm)
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/mdmonitor.service
           └─3052 /sbin/mdadm --monitor --scan

Jan 04 12:47:01 music systemd[1]: Started MD array monitor.
Jan 04 12:47:01 music mdadm[3052]: mdadm: Unknown keyword f
#

ps: used evince to initiate bug report.
let me know if I need to provide more info. Thanks

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: evince 3.26.0-1
ProcVersionSignature: Ubuntu 4.13.0-21.24-lowlatency 4.13.13
Uname: Linux 4.13.0-21-lowlatency x86_64
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
Date: Thu Jan 4 13:22:10 2018
InstallationDate: Installed on 2017-12-30 (5 days ago)
InstallationMedia: Xubuntu 17.10 "Artful Aardvark" - Release amd64 (20171017.1)
ProcEnviron:
 LANGUAGE=en_US
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: evince
UpgradeStatus: No upgrade log present (probably fresh install)