diff --git a/.github/workflows/demo.yml b/.github/workflows/demo.yml
index 37007e2..2d32f03 100644
--- a/.github/workflows/demo.yml
+++ b/.github/workflows/demo.yml
@@ -28,6 +28,8 @@ jobs:
           echo "CI_BASE_REF=$CI_BASE_REF"
           echo "CI_SHA_SHORT=$CI_SHA_SHORT"
           echo "CI_SHA=$CI_SHA"
+          echo "CI_PR_SHA_SHORT=$CI_PR_SHA_SHORT"
+          echo "CI_PR_SHA=$CI_PR_SHA"
           echo "CI_PR_NUMBER=$CI_PR_NUMBER"
           echo "CI_PR_ID=$CI_PR_ID"
           echo "CI_PR_TITLE=$CI_PR_TITLE"
@@ -77,6 +79,8 @@ jobs:
           echo "CI_BASE_REF=$Env:CI_BASE_REF"
           echo "CI_SHA_SHORT=$Env:CI_SHA_SHORT"
           echo "CI_SHA=$Env:CI_SHA"
+          echo "CI_PR_SHA_SHORT=$Env:CI_PR_SHA_SHORT"
+          echo "CI_PR_SHA=$Env:CI_PR_SHA"
           echo "CI_PR_NUMBER=$Env:CI_PR_NUMBER"
           echo "CI_PR_ID=$Env:CI_PR_ID"
           echo "CI_PR_TITLE=$Env:CI_PR_TITLE"
@@ -122,10 +126,11 @@ jobs:
           echo "CI_REF=$CI_REF"
           echo "CI_HEAD_REF_SLUG=$CI_HEAD_REF_SLUG"
           echo "CI_HEAD_REF=$CI_HEAD_REF"
-          echo "CI_BASE_REF_SLUG=$CI_BASE_REF_SLUG"
           echo "CI_BASE_REF=$CI_BASE_REF"
           echo "CI_SHA_SHORT=$CI_SHA_SHORT"
           echo "CI_SHA=$CI_SHA"
+          echo "CI_PR_SHA_SHORT=$CI_PR_SHA_SHORT"
+          echo "CI_PR_SHA=$CI_PR_SHA"
           echo "CI_PR_NUMBER=$CI_PR_NUMBER"
           echo "CI_PR_ID=$CI_PR_ID"
           echo "CI_PR_TITLE=$CI_PR_TITLE"
diff --git a/README.md b/README.md
index 384c263..a7e70e7 100644
--- a/README.md
+++ b/README.md
@@ -30,6 +30,8 @@ A [GitHub Action](https://github.com/features/actions) to expose useful environm
 | `CI_BASE_REF`              | Only set for forked repositories / pull request. The branch of the base repository / the base branch name. Copy of `GITHUB_BASE_REF` - for reasons of completeness. | `main`                                |
 | `CI_SHA_SHORT`             | The shortened commit SHA (8 characters) that triggered the workflow.                                                                                           | `ffac537e`                                 |
 | `CI_SHA`                   | The commit SHA that triggered the workflow. Copy of `GITHUB_SHA` - for reasons of completeness.                                                                | `ffac537e6cbbf934b08745a378932722df287a53` |
+| `CI_PR_SHA_SHORT`          | The shortened latest commit SHA in the pull request's base branch. Short version of `CI_PR_SHA`. Only set for pull requests.                                   | `010b249`                                  |
+| `CI_PR_SHA`                | The latest commit SHA in the pull request's base branch. Long version of `CI_PR_SHA_SHORT`. Only set for pull requests.                                        | `010b2491902d50e8623934f5bc43763ff5991642` |
 | `CI_PR_NUMBER`             | The number of the pull request. Only set for pull requests.                                                                                                    | `42`                                       |
 | `CI_PR_ID`                 | Copy of `CI_PR_NUMBER` for completeness.                                                                                                                       | `42`                                       |
 | `CI_PR_TITLE`              | The title of the pull request. Only set for pull requests.                                                                                                     | `Add feature xyz.`                         |
diff --git a/index.js b/index.js
index 36bbea4..4830fd4 100644
--- a/index.js
+++ b/index.js
@@ -186,6 +186,13 @@ try {
   const pullRequest = github.context.payload &&
       github.context.payload.pull_request;
   if (pullRequest) {
+    const prSha = github.event.pull_request.head.sha;
+    core.exportVariable('CI_PR_SHA_SHORT', getShaShort(prSha));
+    core.info(`Set CI_PR_SHA_SHORT=${process.env.CI_PR_SHA_SHORT}`);
+
+    core.exportVariable('CI_PR_SHA', prSha);
+    core.info(`Set CI_PR_SHA=${process.env.CI_PR_SHA}`);
+
     const prNumber = pullRequest.number;
     core.exportVariable('CI_PR_NUMBER', prNumber);
     core.info(`Set CI_PR_NUMBER=${process.env.CI_PR_NUMBER}`);