Can't get PSDsc (Desired State Configuration) to working in plans in Otter

Hi,
I'm currently evaluating Otter for handling our Configuration Management. We are using Desired State Configuration but I cannot seem to get it to work. I have a set up a simple demo system with 3 roles, 1 server (localhost). Here's the minimum I have to do to reproduce the error. I created a plan for one of the roles with:

##AH:UseTextMode
PSDsc File
(
    Otter_ConfigurationKey: DestinationPath,
    DestinationPath: C:\Windows\,
    Contents: test file ensured
);

This quickly produces an error message:
ERROR: The term 'Invoke-DscResource' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

Am I missing some pre-requisite on my system or am I missing something obvious?

Regards,Hans

Hi Hans... this requires WMF5.0 : https://www.microsoft.com/en-us/download/details.aspx?id=50395