diff --git a/.github/workflows/comment-pr.yaml b/.github/workflows/comment-pr.yaml
index 1e5e93a1..3c20b21b 100644
--- a/.github/workflows/comment-pr.yaml
+++ b/.github/workflows/comment-pr.yaml
@@ -22,6 +22,7 @@ jobs:
             json_diff_file_output: diff.json
             raw_diff_file_output: diff.txt
             file_output_only: "true"
+            base_branch: ${{ github.event.pull_request.base.sha }}
     - name: Show diff
       env:
         DIFF: ${{ steps.git-diff-action.outputs.raw-diff-path }}