--- a/testing/taskcluster/tasks/tests/fx_test_base.yml
+++ b/testing/taskcluster/tasks/tests/fx_test_base.yml
@@ -1,23 +1,33 @@
 ---
 $inherits:
   from: 'tasks/test.yml'
 task:
   workerType: desktop-test
+  scopes:
+    - docker-worker:cache:level-{{level}}-{{project}}-test-workspace
+    - docker-worker:cache:level-{{level}}-{{project}}-test-tmp
   payload:
     image:
       type: 'task-image'
       path: 'public/image.tar'
       taskId: '{{#task_id_for_image}}desktop-test{{/task_id_for_image}}'
     env:
         NEED_WINDOW_MANAGER: true
         NEED_PULSEAUDIO: true
         GECKO_HEAD_REPOSITORY: '{{{head_repository}}}'
         GECKO_HEAD_REV: '{{{head_rev}}}'
+
+    cache:
+      # put the workspace and /tmp on a cache, less for inter-task caching than
+      # to get this directory on fast, non-aufs storage
+      level-{{level}}-{{project}}-test-workspace: '/home/worker/workspace'
+      level-{{level}}-{{project}}-test-tmp: '/tmp'
+
     artifacts:
       'public/test':
         type: directory
         path: '/home/worker/artifacts/'
         expires: '{{#from_now}}1 year{{/from_now}}'
     features:
       allowPtrace: true
   extra: