--- a/taskcluster/taskgraph/transforms/job/__init__.py
+++ b/taskcluster/taskgraph/transforms/job/__init__.py
@@ -147,17 +147,19 @@ def make_task_description(config, jobs):
         if impl:
             job.setdefault('tags', {})['worker-implementation'] = impl
         worker = job.setdefault('worker', {})
         assert 'implementation' not in worker
         worker['implementation'] = impl
         if os:
             worker['os'] = os
 
-        job['run'].setdefault('workdir', '/builds/worker')
+        # always-optimized tasks never execute, so have no workdir
+        if job['run']['using'] != 'always-optimized':
+            job['run'].setdefault('workdir', '/builds/worker')
 
         taskdesc = copy.deepcopy(job)
 
         # fill in some empty defaults to make run implementations easier
         taskdesc.setdefault('attributes', {})
         taskdesc.setdefault('dependencies', {})
         taskdesc.setdefault('routes', [])
         taskdesc.setdefault('scopes', [])