Get the source control git commit ID corresponding to a build ID

Before anyone answer too quickly the Teamcity build change ID is not always the git commit ID. For example if an admin made a configuration change then triggered a build the last change id wont correspond to any git commit. Still in that case I would like to get the git commit ID associated with the build

The GUI can get it there under "build.vcs.number", even if the change was a Teamcity project setting :

b454d000976416331327ed79a2a2071521f1c64c is the last git commit

In the rest api, I found only the lastChanges.change[0].version which sometimes has the git commit id.

fetch({...httpOptions, path:'/app/rest/builds'}).then((response) => {
  const json = response.body;
  for (const build of json.build) {
    fetch({...httpOptions, path:'/app/rest/builds/id:'+build.id}).then((response) => {
      console.log('last change', response.body.lastChanges.change[0], options.gitCommit);
      if (response.body.lastChanges.change[0].version === options.gitCommit) {
        console.log('git commit found', response.body.lastChanges.change[0].version);
        console.log('from build id', build.id);
        download({...httpOptions, path:'/app/rest/builds/id:'+build.id+'/artifacts/archived'}, "./artifact."+options.gitCommit+".zip");
      }
(...)

For that build matching the gui screenshot, the lastChange.change[0].version value is deb426c28d7d8c55c8e7a706c5c07231de8e3e55 which is not the git commit id.

So where do I get the consistent git commit ID associated with a build ID in the Teamcity REST API ?

Thanks!