diff --git a/.taskcluster.yml b/.taskcluster.yml
index 4c13342a367..2ea418acc9e 100644
--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -5,43 +5,45 @@ policy:
 tasks:
   - $if: 'tasks_for == "github-push"'
     then:
-      taskGroupId: {$eval: as_slugid("decision_task")}
-      taskId: {$eval: as_slugid("decision_task")}
-      provisionerId: aws-provisioner-v1
-      workerType: servo-docker-worker
-      created: {$fromNow: ''}
-      deadline: {$fromNow: '1 day'}
-      metadata:
-        name: "Taskcluster experiments for Servo: decision task"
-        description: ""
-        owner: ${event.pusher.name}@users.noreply.github.com
-        source: ${event.compare}
-      scopes:
-        - "queue:scheduler-id:taskcluster-github"
+      $if: 'event.ref == "refs/heads/master"'
+      then:
+        taskGroupId: {$eval: as_slugid("decision_task")}
+        taskId: {$eval: as_slugid("decision_task")}
+        provisionerId: aws-provisioner-v1
+        workerType: servo-docker-worker
+        created: {$fromNow: ''}
+        deadline: {$fromNow: '1 day'}
+        metadata:
+          name: "Taskcluster experiments for Servo: decision task"
+          description: ""
+          owner: ${event.pusher.name}@users.noreply.github.com
+          source: ${event.compare}
+        scopes:
+          - "queue:scheduler-id:taskcluster-github"
 
-        # Granted to role "repo:github.com/servo/servo-taskcluster-experiments:branch:master"
-        - "queue:create-task:highest:aws-provisioner-v1/servo-*"
-        - "docker-worker:cache:cargo-registry-cache"
-        - "docker-worker:cache:cargo-git-cache"
-        - "queue:route:index.project.servo.servo-taskcluster-experiments.*"
+          # Granted to role "repo:github.com/servo/servo-taskcluster-experiments:branch:master"
+          - "queue:create-task:highest:aws-provisioner-v1/servo-*"
+          - "docker-worker:cache:cargo-registry-cache"
+          - "docker-worker:cache:cargo-git-cache"
+          - "queue:route:index.project.servo.servo-taskcluster-experiments.*"
 
-      payload:
-        maxRunTime: {$eval: '20 * 60'}
-        # https://github.com/servo/taskcluster-bootstrap-docker-images#decision-task
-        image: "servobrowser/taskcluster-bootstrap:decision-task@sha256:28045b7ec0485ef363f8cb14f194008b47e9ede99f2ea40a1e945e921fce976e"
-        features:
-          taskclusterProxy: true
-        env:
-          GITHUB_EVENT_OWNER: ${event.pusher.name}@users.noreply.github.com
-          GITHUB_EVENT_SOURCE: ${event.compare}
-          GITHUB_EVENT_CLONE_URL: ${event.repository.clone_url}
-          GITHUB_EVENT_COMMIT_SHA: ${event.after}
-        command:
-          - /bin/bash
-          - '--login'
-          - '-c'
-          - >-
-            git clone $GITHUB_EVENT_CLONE_URL repo &&
-            cd repo &&
-            git checkout $GITHUB_EVENT_COMMIT_SHA &&
-            python3 decision-task.py
+        payload:
+          maxRunTime: {$eval: '20 * 60'}
+          # https://github.com/servo/taskcluster-bootstrap-docker-images#decision-task
+          image: "servobrowser/taskcluster-bootstrap:decision-task@sha256:28045b7ec0485ef363f8cb14f194008b47e9ede99f2ea40a1e945e921fce976e"
+          features:
+            taskclusterProxy: true
+          env:
+            GITHUB_EVENT_OWNER: ${event.pusher.name}@users.noreply.github.com
+            GITHUB_EVENT_SOURCE: ${event.compare}
+            GITHUB_EVENT_CLONE_URL: ${event.repository.clone_url}
+            GITHUB_EVENT_COMMIT_SHA: ${event.after}
+          command:
+            - /bin/bash
+            - '--login'
+            - '-c'
+            - >-
+              git clone $GITHUB_EVENT_CLONE_URL repo &&
+              cd repo &&
+              git checkout $GITHUB_EVENT_COMMIT_SHA &&
+              python3 decision-task.py
diff --git a/decisionlib.py b/decisionlib.py
index 8064d78180c..b8ea250c394 100644
--- a/decisionlib.py
+++ b/decisionlib.py
@@ -30,6 +30,7 @@ class DecisionTask:
         # https://docs.taskcluster.net/docs/reference/workers/docker-worker/docs/features#feature-taskclusterproxy
         self.queue_service = taskcluster.Queue(options={"baseUrl": "http://taskcluster/queue/v1/"})
         self.index_service = taskcluster.Index(options={"baseUrl": "http://taskcluster/index/v1/"})
+
         self.now = datetime.datetime.utcnow()
 
     def from_now_json(self, offset):