Template creation fails if /var/tmp is xfs

Template creation fails if /var/tmp is xfs, which is the default file system on RHEL7. The documentation for installation does not highlight this requirement for /var/tmp; it does for /vz though. Reference:
https://openvz.org/Quick_installation

Here is the full output. Resolved by formatting /var/tmp with ext4 instead of xfs.

My version:
[root@cluster-02 ~]# rpm -q vztt
vztt-7.0.28-1.vz7.x86_64

[root@cluster-02 ~]# vzpkg update cache centos-7-x86_64
Update OS template cache for centos-7-x86_64 template
Cleaning repos: base0 base1 base2 base3
0 metadata files removed
0 sqlite files removed
0 metadata files removed
base0 | 951 B 00:00:00
base1 | 951 B 00:00:00
base2 | 3.6 kB 00:00:00
base3 | 3.4 kB 00:00:00
(1/8): base2/group_gz | 155 kB 00:00:00
(2/8): base3/filelists_db | 1.5 MB 00:00:00
(3/8): base3/primary_db | 2.3 MB 00:00:00
(4/8): base2/primary_db | 5.3 MB 00:00:01
(5/8): base3/prestodelta | 161 kB 00:00:00
(6/8): base2/filelists_db | 6.2 MB 00:00:01
(7/8): base2/other_db | 2.3 MB 00:00:03
(8/8): base3/other_db | 19 MB 00:00:02
(1/6): base0/filelists | 326 B 00:00:00
(2/6): base0/primary | 723 B 00:00:00
(3/6): base0/other | 309 B 00:00:00
(4/6): base1/filelists | 150 B 00:00:00
(5/6): base1/primary | 157 B 00:00:00
(6/6): base1/other | 145 B 00:00:00
base0 1/1
base0 1/1
base0 1/1
Metadata Cache Created
Cleaning repos: docker0
0 metadata files removed
0 sqlite files removed
0 metadata files removed
docker0 | 3.4 kB 00:00:00
(1/4): docker0/filelists_db | 246 kB 00:00:00
(2/4): docker0/other_db | 256 kB 00:00:00
(3/4): docker0/primary_db | 90 kB 00:00:00
(4/4): docker0/prestodelta | 16 kB 00:00:01
Metadata Cache Created
Error: Failed to create ploop image /var/tmp//vzpkg.vrDKJ9/cache-private/root.hdd/root.hds: Error in add_delta (ploop.c:1345): Can't add image /var/tmp//vzpkg.vrDKJ9/cache-private/root.hdd/root.hds: unsupported underlying filesystem 3
Error: Cannot create ploop device