diff --git a/.taskcluster.yml b/.taskcluster.yml
index 8116488b8..b7f10ba06 100644
--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -12,6 +12,10 @@ tasks:
         expires_in: {$fromNow: '1 year'}
         repository: ${event.repository.html_url}
         scheduler_id: focus-nightly-sched
+
+        head_rev: ${event.release.tag_name}
+        head_branch: ${event.release.target_commitish}
+
         is_mozilla_mobile_repo:
           $eval: event.repository.html_url == 'https://github.com/mozilla-mobile/fenix'
         track:
@@ -26,6 +30,7 @@ tasks:
           $if: event.repository.html_url == 'https://github.com/mozilla-mobile/fenix'
           then: mobile-3-b-fenix
           else: mobile-1-b-fenix
+
       in:
         taskId: ${decision_task_id}
         taskGroupId: ${decision_task_id}  # Must be explicit because of Chain of Trust
@@ -66,9 +71,9 @@ tasks:
             chainOfTrust: true
           env:
             BUILD_WORKER_TYPE: ${build_worker_type}
-            MOBILE_HEAD_BRANCH: ${event.release.target_commitish}
+            MOBILE_HEAD_BRANCH: ${head_branch}
             MOBILE_HEAD_REPOSITORY: ${repository}
-            MOBILE_HEAD_REV: ${event.release.tag_name}
+            MOBILE_HEAD_REV: ${head_rev}
             MOBILE_TRIGGERED_BY: ${event.sender.login}
             SCHEDULER_ID: ${scheduler_id}
             TASK_ID: ${decision_task_id}
@@ -77,28 +82,28 @@ tasks:
             - --login
             - -cx
             - >-
-              cd ..
-              && git clone ${repository} repository
-              && cd repository
+              git fetch ${repository} ${head_branch}
+              && git config advice.detachedHead false
+              && git checkout ${head_rev}
               && python automation/taskcluster/decision_task_nightly.py \
                 --track ${track} \
                 --commit \
-                --output /opt/repository/app/build/outputs/apk \
+                --output /opt/fenix/app/build/outputs/apk \
                 --apk arm/release/app-arm-release-unsigned.apk \
                 --apk x86/release/app-x86-release-unsigned.apk \
                 --date ${now}
           artifacts:
             public/task-graph.json:
               type: file
-              path: /opt/repository/task-graph.json
+              path: /opt/fenix/task-graph.json
               expires: ${expires_in}
             public/actions.json:
               type: file
-              path: /opt/repository/actions.json
+              path: /opt/fenix/actions.json
               expires: ${expires_in}
             public/parameters.yml:
               type: file
-              path: /opt/repository/parameters.yml
+              path: /opt/fenix/parameters.yml
               expires: ${expires_in}
         extra:
           cron: {$json: {$eval: 'cron'}}
@@ -107,4 +112,4 @@ tasks:
           name: Fenix Nightly Decision Task
           description: Decision task scheduled by cron task [${cron.task_id}](https://tools.taskcluster.net/tasks/${cron.task_id})
           owner: ${event.sender.login}@users.noreply.github.com
-          source: ${repository}/raw/${event.release.tag_name}/.taskcluster.yml
+          source: ${repository}/raw/${head_rev}/.taskcluster.yml
diff --git a/automation/taskcluster/decision_task_nightly.py b/automation/taskcluster/decision_task_nightly.py
index 963e5ad32..a573e0ba9 100644
--- a/automation/taskcluster/decision_task_nightly.py
+++ b/automation/taskcluster/decision_task_nightly.py
@@ -19,6 +19,7 @@ TASK_ID = os.environ.get('TASK_ID')
 SCHEDULER_ID = os.environ.get('SCHEDULER_ID')
 GITHUB_HTTP_REPOSITORY = os.environ.get('MOBILE_HEAD_REPOSITORY')
 HEAD_REV = os.environ.get('MOBILE_HEAD_REV')
+HEAD_BRANCH = os.environ.get('MOBILE_HEAD_BRANCH')
 
 BUILDER = lib.tasks.TaskBuilder(
     task_id=TASK_ID,
@@ -36,13 +37,20 @@ def generate_build_task(apks, is_staging):
         "expires": taskcluster.stringDate(taskcluster.fromNow('1 year')),
     } for apk in apks}
 
-    checkout = 'git clone {} repository && cd repository'.format(GITHUB_HTTP_REPOSITORY)
+    checkout = (
+        "export TERM=dumb && git fetch {} {} --tags && "
+        "git config advice.detachedHead false && "
+        "git checkout {}".format(
+            GITHUB_HTTP_REPOSITORY, HEAD_BRANCH, HEAD_REV
+        )
+    )
     sentry_secret = '{}project/mobile/fenix/sentry'.format('garbage/staging/' if is_staging else '')
 
     return taskcluster.slugId(), BUILDER.build_task(
         name="(Fenix) Build task",
         description="Build Fenix from source code.",
-        command=('cd .. && ' + checkout +
+        command=(
+            checkout +
             ' && python automation/taskcluster/helper/get-secret.py'
             ' -s {} -k dsn -f .sentry_token'.format(sentry_secret) +
             ' && ./gradlew --no-daemon -PcrashReports=true clean test assembleRelease'),