--- a/taskcluster/taskgraph/transforms/job/mach.py
+++ b/taskcluster/taskgraph/transforms/job/mach.py
@@ -11,16 +11,20 @@ from taskgraph.transforms.job import run
 from taskgraph.util.schema import Schema
 from voluptuous import Required
 
 mach_schema = Schema({
     Required('using'): 'mach',
 
     # The mach command (omitting `./mach`) to run
     Required('mach'): basestring,
+
+    # if true, perform a checkout of a comm-central based branch inside the
+    # gecko checkout
+    Required('comm-checkout', default=False): bool,
 })
 
 
 @run_job_using("docker-worker", "mach", schema=mach_schema)
 @run_job_using("native-engine", "mach", schema=mach_schema)
 def docker_worker_mach(config, job, taskdesc):
     run = job['run']