diff --git a/.github/workflows/pr_review_plan_comment.yml b/.github/workflows/pr_review_plan_comment.yml
index e877bcbc..400f1ff1 100644
--- a/.github/workflows/pr_review_plan_comment.yml
+++ b/.github/workflows/pr_review_plan_comment.yml
@@ -16,7 +16,8 @@ jobs:
       - name: Checkout trusted base code
         uses: actions/checkout@v4
         with:
-          ref: ${{ github.event.pull_request.base.sha }}
+          # Keep the workflow and helper script versions in sync while avoiding fork code.
+          ref: ${{ github.event.pull_request.base.ref }}
 
       - name: Set up Python
         uses: actions/setup-python@v5