Getting an error from miniapi add_result

I'm attempting to post test results using the miniapi add_result method, but I'm getting the following error:

{
    "result": false,
    "error": "[Microsoft][SQL Server Native Client 11.0][SQL Server]Conversion failed when converting the nvarchar value 'api' to data type int."
}

The post looks like this:

http://sea1testrail01/testrail/index.php?/miniapi/add_result/1258&key=lsdkf90234kjlkjas999893824

Post parameters: status_id=1

I've successfully gotten results back from the miniapi for other GET and POST calls, so I'm not sure what to make of this.

Any ideas as to how to fix this?