diff --git a/.github/workflows/pre-commit.yaml b/.github/workflows/pre-commit.yaml
index 6b4bf6a8..59ea9028 100644
--- a/.github/workflows/pre-commit.yaml
+++ b/.github/workflows/pre-commit.yaml
@@ -40,6 +40,10 @@ jobs:
       - name: Checkout git repository
         uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
         with:
+          # For fork PRs the head branch only exists on the fork, so the
+          # repository must point at the fork or the checkout fails. Falls
+          # back to the base repo for non-pull_request events.
+          repository: ${{ github.event.pull_request.head.repo.full_name || github.repository }}
           ref: ${{ github.event.pull_request.head.ref || github.ref }}
           persist-credentials: false