diff --git a/README.md b/README.md
index 745ee8a..e31dc44 100644
--- a/README.md
+++ b/README.md
@@ -117,6 +117,7 @@ Refer [here](https://github.com/actions/checkout/blob/v1/README.md) for previous
 - [Checkout multiple repos (private)](#Checkout-multiple-repos-private)
 - [Checkout pull request HEAD commit instead of merge commit](#Checkout-pull-request-HEAD-commit-instead-of-merge-commit)
 - [Checkout pull request on closed event](#Checkout-pull-request-on-closed-event)
+- [Fetch pull request base-ref in addition to merge commit (for diffing)](#Fetch-pull-request-base-ref-in-addition-to-merge-commit-for-diffing)
 - [Fetch all tags](#Fetch-all-tags)
 - [Fetch all branches](#Fetch-all-branches)
 - [Fetch all history for all tags and branches](#Fetch-all-history-for-all-tags-and-branches)
@@ -207,6 +208,15 @@ jobs:
       - uses: actions/checkout@v2
 ```
 
+## Fetch pull request base-ref in addition to merge commit (for diffing)
+
+```yml
+- uses: actions/checkout@v2
+- name: Fetch base_ref HEAD
+  run: git fetch --depth=1 origin +refs/heads/${{github.base_ref}}:refs/remotes/origin/${{github.base_ref}}
+- run: git diff origin/${{github.base_ref}}..HEAD
+```
+
 ## Fetch all tags
 
 ```yaml