--- a/taskcluster/taskgraph/transforms/job/mozharness.py
+++ b/taskcluster/taskgraph/transforms/job/mozharness.py
@@ -144,16 +144,17 @@ def mozharness_on_docker_worker_setup(co
                                       extra=run.get('extra-workspace-cache-key'))
     support_vcs_checkout(config, job, taskdesc)
 
     env = worker.setdefault('env', {})
     env.update({
         'MOZHARNESS_CONFIG': ' '.join(run['config']),
         'MOZHARNESS_SCRIPT': run['script'],
         'MH_BRANCH': config.params['project'],
+        'MOZ_SOURCE_CHANGESET': env['GECKO_HEAD_REV'],
         'MH_BUILD_POOL': 'taskcluster',
         'MOZ_BUILD_DATE': config.params['moz_build_date'],
         'MOZ_SCM_LEVEL': config.params['level'],
         'MOZ_AUTOMATION': '1',
     })
 
     if 'actions' in run:
         env['MOZHARNESS_ACTIONS'] = ' '.join(run['actions'])
@@ -240,16 +241,18 @@ def mozharness_on_generic_worker(config,
 
     docker_worker_add_gecko_vcs_env_vars(config, job, taskdesc)
 
     env = worker['env']
     env.update({
         'MOZ_BUILD_DATE': config.params['moz_build_date'],
         'MOZ_SCM_LEVEL': config.params['level'],
         'MOZ_AUTOMATION': '1',
+        'MH_BRANCH': config.params['project'],
+        'MOZ_SOURCE_CHANGESET': env['GECKO_HEAD_REV'],
     })
     if run['use-simple-package']:
         env.update({'MOZ_SIMPLE_PACKAGE_NAME': 'target'})
 
     if 'extra-config' in run:
         env['EXTRA_MOZHARNESS_CONFIG'] = json.dumps(run['extra-config'])
 
     # The windows generic worker uses batch files to pass environment variables