diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 71f45b0..c0cec40 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -19,13 +19,15 @@ jobs:
       src: ${{ steps.filter.outputs.src }}
     steps:
       - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
       - name: Check for non-doc changes
         id: filter
         run: |
           BASE=${{ github.event.pull_request.base.sha }}
           HEAD=${{ github.sha }}
-          CHANGED=$(git diff --name-only "$BASE" "$HEAD" 2>/dev/null || git diff --name-only HEAD~1 HEAD)
-          NON_DOC=$(echo "$CHANGED" | grep -vE '^(README\.md|\.gitignore|LICENSE)$' || true)
+          CHANGED=$(git diff --name-only "${BASE:-HEAD~1}" "$HEAD")
+          NON_DOC=$(echo "$CHANGED" | grep -vE '(^|/)README\.md$|^\.gitignore$|^LICENSE$' || true)
           if [ -n "$NON_DOC" ]; then
             echo "src=true" >> $GITHUB_OUTPUT
           else