[SOLVED] ActiveCollab Update invoice status using API v1

Following the Documentation I've tried to update the status of an invoice using the API.

I've tried to send

{"single": {"status": "$status"}} as well as just

{"status": "$status"} to

PUT api/v1/invoices/$invoiceId

where $status is canceled (also tried with paid) but without success. Although I get a http status code of 200 back, in all cases. How can I "cancel" an invoice? And how about sending an "Illegal Request" status code or something, if the request fails?

Thanks, Martin.

{"application":"ActiveCollab","version":"6.0.6"}