--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -102,17 +102,19 @@ tasks:
               COMM_BASE_REPOSITORY: 'https://hg.mozilla.org/comm-central'
               COMM_HEAD_REPOSITORY: '${repoUrl}'
               COMM_HEAD_REF: '${push.revision}'
               COMM_HEAD_REV: '${push.revision}'
               HG_STORE_PATH: /buillds/worker/checkouts/hg-store
               TASKCLUSTER_CACHES: /builds/worker/checkouts
             - $if: 'tasks_for != "action"'
               then:
-                COMM_COMMIT_MSG: '${push.comment}'
+                # scriptworker expects an environment variable named GECKO_COMMIT_MSG,
+                # see: https://github.com/mozilla-releng/scriptworker/blob/master/scriptworker/task.py
+                GECKO_COMMIT_MSG: '${push.comment}'
             - $if: 'tasks_for == "action"'
               then:
                 ACTION_TASK_GROUP_ID: '${ownTaskId}'
                 ACTION_TASK_ID: {$json: {$eval: 'taskId'}}
                 ACTION_TASK: {$json: {$eval: 'task'}}
                 ACTION_INPUT: {$json: {$eval: 'input'}}
                 ACTION_CALLBACK: '${action.cb_name}'
                 ACTION_PARAMETERS: {$json: {$eval: 'parameters'}}
@@ -154,17 +156,17 @@ tasks:
               else: >
                 cd /builds/worker/checkouts/gecko &&
                 ln -s /builds/worker/artifacts artifacts &&
                 ./mach --log-no-times taskgraph decision
                 --root=comm/taskcluster/ci
                 --pushlog-id='${push.pushlog_id}'
                 --pushdate='${push.pushdate}'
                 --project='${repository.project}'
-                --message="$COMM_COMMIT_MSG"
+                --message="$GECKO_COMMIT_MSG"
                 --owner='${ownerEmail}'
                 --level='${repository.level}'
                 --base-repository="$GECKO_BASE_REPOSITORY"
                 --head-repository="$GECKO_HEAD_REPOSITORY"
                 --head-ref="$GECKO_HEAD_REF"
                 --head-rev="$GECKO_HEAD_REV"
                 --comm-base-repository="$COMM_BASE_REPOSITORY"
                 --comm-head-repository="$COMM_HEAD_REPOSITORY"