Strange parsing for oneimage

[gdhgdhgdh]

Given Puppet 3.7.4, CentOS 7 and hiera config:

oneimages:
  test-image:
    datastore: cephstore
    type: datablock
    persistent: true
    dev_prefix: vd
    driver: raw
    disk_type: RBD
    size: 4096
    fstype: raw

and this fragment in a Puppet manifest:

  create_resources(oneimage, hiera_hash(oneimages))

I get the following segment of output:

Debug: Prefetching cli resources for oneimage
Debug: Executing '/usr/bin/oneimage list -x'
Error: Could not set 'present' on ensure: undefined method `to_s_upcase' for :DATABLOCK:Symbol
Error: Could not set 'present' on ensure: undefined method `to_s_upcase' for :DATABLOCK:Symbol
Wrapped exception:
undefined method `to_s_upcase' for :DATABLOCK:Symbol
Error: /Stage[main]/Roles::Onevm/Oneimage[test-image]/ensure: change from absent to present failed: Could not set 'present' on ensure: undefined method `to_s_upcase' for :DATABLOCK:Symbol

All of my current disks are DATABLOCK <TYPE>2</TYPE>, and I did try to add a mapping 2 => DATABLOCK at line 100 of lib/puppet/provider/oneimage/cli.rb but it made no difference - I don't understand enough Ruby to see the logic of what's being attempted :/

Cheers,
Gavin.