Get list of task with nu assignees gives error

When I try to get a list of task including (or just only) task with no assignee I get the following error.
Also tried only -1 as a parameter, but that also does not work.

GET /task/?assigneeid=-1

And according to the API documentation (https://www.myintervals.com/api/resource.php?r=task) I should be able to give -1 as a parameter.

Any idea if I am doing something wrong, or is it at your side?

"error": {
"code": 18,
"message": "Validation error has occurred (missing required field/parameter, or bad field/parameter)",
"verbose": [
"Validation failed for the value (-1,116288) passed to the following field: assigneeid",
"This field expects a numeric value. If you are trying to pass multiple values to this field, they should be in CSV format, and should contain only integers and commas (ie. spaces are not permitted).",
"Please consult the API documentation at https://myintervals.com/api for more information or email API support at api@myintervals.com for help."
]"

icvanee,

Our development team has deployed an update that should fix the problem. Please give it a try and let us know if you need any other assistance.