pressing key TAB after ipset gives syntax error in bash interactive session

[LGB [Gábor Lénárt]]

After typing ipset (and a space of course) I always get various syntax error messages if I press key TAB for completion. Interestingly I get different errors on different machines, for example:

18.04 server:

# ipset
So I typed "ipset" and a space, and when I press TAB, I see this:
# ipset bash: syntax error near unexpected token `;;'

18.04 xubuntu install:

# ipset
again, I typed "ipset" and space, and I pressed TAB:
# ipset bash: syntax error in conditional expression

18.04 ubuntu install:

(the same as before, when I press tab)
# ipset bash: syntax error in conditional expression
bash: syntax error near `213_stat'

(213_stat is maybe a file name by the way, since I have a file named 213_stat in the current working directory)

By the way, this also applies when I'm different context of the command, ie:

# ipset save
"ipset save" and a space, pressing TAB:
# ipset save bash: syntax error near unexpected token `;;'

It seems, if the current command line is anything to do with ipset, it causes errors on trying completion

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: bash-completion 1:2.8-1ubuntu1
ProcVersionSignature: Ubuntu 4.15.0-53.57-generic 4.15.18
Uname: Linux 4.15.0-53-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: XFCE
Date: Mon Jun 24 00:49:44 2019
Dependencies:

InstallationDate: Installed on 2015-07-10 (1444 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release i386 (20150422)
PackageArchitecture: all
SourcePackage: bash-completion
UpgradeStatus: Upgraded to bionic on 2017-06-20 (733 days ago)