How to set a field to Null in the Box API

Hi Everyone,

I'm trying to set a field to null in the Box API. I tried the REST standard

'fieldsToNull', but that does not seem to work.

I would like to set the field to the state before data was added to the field. I tried setting it to an empty string, but that, as expected, stores the empty string '' and not Null.

Is there a way to do this?

I'm trying to clear out the 'provenance' field in a group object.

Thanks,
Mike