Closing merge request using api doesn`t work after upgrade from 8.13 to 8.14

Summary

Im closing merge request using api via PUT /projects/:id/merge_requests/:merge_request_id like it described in documentation. After upgrade my code doesnt work anymore

Steps to reproduce

Close merge request using PUT /projects/:id/merge_requests/:merge_request_id

Expected behavior

Merge request closed successfully.

Actual behavior

Method returns 400 http error

Relevant logs and/or screenshots

Code from NGitLab.NET project http://www.screencast.com/t/6ksl22dEd8R