API endpoint for {repo_slug} using PUT method does not allow parsing the mainbranch attribute

As the title says, through the API today parsing the "mainbranch" attribute using the PUT method does absolutely nothing, the API gives a 200 code and does not alter the attribute within the repository
The expected behavior in this case is for the attribute "mainbranch" to be updated parsing it through a json, like this:

#!bash


curl PUT -u <userAuthString> -H "Content-Type: application/json" https://api.bitbucket.org/2.0/repositories/<repo_slug>-d &#x27;{"mainbranch": { "type":"branch", "name": "<newmainbranch>"}}&#x27;