diff --git a/.github/workflows/tools.yml b/.github/workflows/tools.yml
index e5ea38b755c3..b5a38cf9a233 100644
--- a/.github/workflows/tools.yml
+++ b/.github/workflows/tools.yml
@@ -336,7 +336,7 @@ jobs:
         # no-op if the base branch is already up-to-date.
         with:
           token: ${{ secrets.GH_USER_TOKEN }}
-          branch: actions/${{ github.ref_name == 'main' || format('{0}/', github.ref_name) }}tools-update-${{ matrix.id }}  # Custom branch *just* for this Action.
+          branch: actions/${{ github.ref_name != 'main' && format('{0}/', github.ref_name) || '' }}tools-update-${{ matrix.id }}  # Custom branch *just* for this Action.
           delete-branch: true
           commit-message: ${{ env.COMMIT_MSG }}
           labels: ${{ matrix.label }}