Error when purging local users on Windows

This a significant user.

FROM THE USER:

We want to control the local users with Puppet and purge any unmanaged user for audit compliance and security purposes. When I configure this in the below manifest I get the following error:
Error: /Stage[main]/Main/Resources[user]: Failed to generate additional resources using 'generate': comparison of String with 499 failed
Can this please be fixed.

user

{ ['Administrator', 'guest']: ensure => present }

resources

{ 'user': purge => true }

As a generic rule of thumb you can expect us to use Puppet and all classes on every Windows edition available from 2003 and up, although 2008 and up is really the current scope, don't care too much about 2003. I just tested and this doesn't work on Windows 2012R2 either. I've never tested it before, we're in the process of putting this compliancy rule in Puppet so this is the first time I run into this. It looks like a bug to me, tt work fine (as expected) for for example the group resource or host resource and even type/providers we created ourselves.