IPv6 value in httpd's proxy_ips is breaking horizon

The following error appears in OVB jobs [1]:

2019-03-08 03:53:04 | "Error: Evaluation Error: Error while evaluating a Function Call, Class[Apache::Mod::Remoteip]: parameter 'proxy_ips' index 0 expects a Stdlib::Host = Variant[Stdlib::Fqdn = Pattern[/^(([a-zA-Z0-9]|[a-zA-Z0-9][a-zA-Z0-9\\-]*[a-zA-Z0-9])\\.)*([A-Za-z0-9]|[A-Za-z0-9][A-Za-z0-9\\-]*[A-Za-z0-9])$/], Stdlib::Compat::Ip_address = Variant[Stdlib::Compat::Ipv4 = Pattern[/^((([0-9](?!\\d)|[1-9][0-9](?!\\d)|1[0-9]{2}(?!\\d)|2[0-4][0-9](?!\\d)|25[0-5](?!\\d))[.]){3}([0-9](?!\\d)|[1-9][0-9](?!\\d)|1[0-9]{2}(?!\\d)|2[0-4][0-9](?!\\d)|25[0-5](?!\\d)))(\\/((([0-9](?!\\d)|[1-9][0-9](?!\\d)|1[0-9]{2}(?!\\d)|2[0-4][0-9](?!\\d)|25[0-5](?!\\d))[.]){3}([0-9](?!\\d)|[1-9][0-9](?!\\d)|1[0-9]{2}(?!\\d)|2[0-4][0-9](?!\\d)|25[0-5](?!\\d))|[0-9]+))?$/], Stdlib::Compat::Ipv6 = Pattern[/\\s*((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)(\\.(25[0-5]|2[0-4]\\d|1\\d\\d|[1-9]?\\d)){3}))|:)))(%.+)?\\s*$/]]] value, got String (file: /etc/puppet/modules/tripleo/manifests/profile/base/horizon.pp, line: 88, column: 5) on node overcloud-controller-0.localdomain",

Checking the value that was breaking; it seems to be an IPv6 CIDR:

    "apache::mod::remoteip::proxy_ips": [
        "fd00:fd00:fd00:2000::/64"
    ],

This gives an error in the deployment of horizon.

[1] http://logs.rdoproject.org/60/641660/2/openstack-check/tripleo-ci-centos-7-ovb-3ctlr_1comp-featureset035/3529e09/logs/undercloud/home/zuul/overcloud_deploy.log.txt.gz