diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 1d90d6f..177b8b4 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -30,6 +30,10 @@ jobs:
       - uses: actions/checkout@v4
         with:
           ref: ${{ inputs.ref }}
+          # Full history: the default shallow fetch resolves `ref` as a branch
+          # or tag glob, so an arbitrary commit SHA cannot be checked out — and
+          # deploying a specific commit is exactly how a rollback is performed.
+          fetch-depth: 0
 
       - name: Record what is being deployed
         id: meta