This used to work:

p4sync credential: 'p4integ.prod',
  populate: previewOnly(quiet: true, pin: env.latest_version),
  source: depotSource('//foo/bar/playbooks')

Now it produces the following error message:

... p4 client -o jenkins-master-scm-promote_ansible_playbooks-0 +
... p4 client -i +
P4: Unable to setup workspace: com.perforce.p4java.exception.RequestException: Error in client specification.
Mapping '//jenkins-master-scm/promote_ansible_playbooks-0/...' is not under '//jenkins-master-scm-promote_ansible_playbooks-0/...'.

Notice that the client name is properly replaced in the p4 client call, but not in the actual client view.