vault:certificate relation doesn't work when using IPv6

With vault (1.5.9 from charmhub/stable rev 50), the vault:vertificate relation doesn't work if using IPv6 as cert issuance fails with:

unit-vault-0: 14:02:38 INFO unit.vault/0.juju-log Invoking reactive handler: reactive/vault_handlers.py:869:auto_generate_root_ca_cert
unit-vault-0: 14:02:39 ERROR unit.vault/0.juju-log Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-vault-0/charm/reactive/vault_handlers.py", line 882, in auto_generate_root_ca_cert
    root_ca = vault_pki.generate_root_ca(
  File "/var/lib/juju/agents/unit-vault-0/charm/lib/charm/vault_pki.py", line 280, in generate_root_ca
    client.write(
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/hvac/v1/__init__.py", line 189, in write
    response = self._adapter.post('/v1/{0}'.format(path), json=kwargs, wrap_ttl=wrap_ttl)
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/hvac/adapters.py", line 103, in post
    return self.request('post', url, **kwargs)
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/hvac/adapters.py", line 233, in request
    utils.raise_for_error(response.status_code, text, errors=errors)
  File "/var/lib/juju/agents/unit-vault-0/.venv/lib/python3.8/site-packages/hvac/utils.py", line 29, in raise_for_error
    raise exceptions.InvalidRequest(message, errors=errors)
hvac.exceptions.InvalidRequest: invalid URL found in issuing certificates: http://2602:fc62:b:1018:1::f770:8200/v1/charm-pki-local/ca