diff --git a/action.yml b/action.yml
index 9af600be..31330112 100644
--- a/action.yml
+++ b/action.yml
@@ -175,6 +175,7 @@ runs:
         GITHUB_WORKSPACE: ${{ github.workspace }}
         GITHUB_EVENT_HEAD_REPO_FORK: ${{ github.event.pull_request.head.repo.fork }}
         GITHUB_EVENT_PULL_REQUEST_BASE_SHA: ${{ github.event.pull_request.base.sha }}
+        GITHUB_EVENT_PULL_REQUEST_HEAD_SHA: ${{ github.event.pull_request.head.sha }}
         GITHUB_EVENT_BEFORE: ${{ github.event.before }}
         GITHUB_EVENT_FORCED: ${{ github.event.forced }}
         GITHUB_REFNAME: ${{ github.ref_name }}