diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e45ce5f..1f6d1e4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,8 +38,20 @@ jobs:
                libclang$LLVM_TAG-dev \
                clang$LLVM_TAG
 
-      - name: Check out default branch
-        uses: actions/checkout@v2
+      - name: Select checkout ref (PR)
+        if: github.event_name == 'pull_request'
+        run: |
+          echo "IWYU_CHECKOUT_REF=${{github.event.pull_request.head.sha}}" >> $GITHUB_ENV
+
+      - name: Select checkout ref (push/schedule)
+        if: github.event_name == 'push' || github.event_name == 'schedule'
+        run: |
+          echo "IWYU_CHECKOUT_REF=${{github.sha}}" >> $GITHUB_ENV
+
+      - name: Check out branch
+        uses: actions/checkout@v3
+        with:
+          ref: ${{env.IWYU_CHECKOUT_REF}}
 
       - name: Build include-what-you-use
         run: |