--- a/taskcluster/mach_commands.py
+++ b/taskcluster/mach_commands.py
@@ -169,24 +169,24 @@ class MachCommands(MachCommandBase):
             return taskgraph.decision.taskgraph_decision(options)
         except Exception:
             traceback.print_exc()
             sys.exit(1)
 
     @SubCommand('taskgraph', 'cron',
                 description="Run the cron task")
     @CommandArgument('--base-repository',
-                     required=True,
-                     help='URL for "base" repository to clone')
+                     required=False,
+                     help='(ignored)')
     @CommandArgument('--head-repository',
                      required=True,
                      help='URL for "head" repository to fetch')
     @CommandArgument('--head-ref',
-                     required=True,
-                     help='Reference to fetch in head-repository (usually "default")')
+                     required=False,
+                     help='(ignored)')
     @CommandArgument('--project',
                      required=True,
                      help='Project to use for creating tasks. Example: --project=mozilla-central')
     @CommandArgument('--level',
                      required=True,
                      help='SCM level of this repository')
     @CommandArgument('--force-run',
                      required=False,

--- a/taskcluster/taskgraph/cron/__init__.py
+++ b/taskcluster/taskgraph/cron/__init__.py
@@ -121,23 +121,18 @@ def calculate_time(options):
 
 
 def taskgraph_cron(options):
     params = {
         # name of this cron job (set per job below)
         'job_name': '..',
 
         # repositories
-        'base_repository': options['base_repository'],
         'head_repository': options['head_repository'],
 
-        # the symbolic ref this should run against (which happens to be what
-        # run-task checked out for us)
-        'head_ref': options['head_ref'],
-
         # *calculated* head_rev; this is based on the current meaning of this
         # reference in the working copy
         'head_rev': calculate_head_rev(options),
 
         # the project (short name for the repository) and its SCM level
         'project': options['project'],
         'level': options['level'],