diff --git a/.github/workflows/dependabot-deploy.yml b/.github/workflows/dependabot-deploy.yml
index 2be00da..0d6074b 100644
--- a/.github/workflows/dependabot-deploy.yml
+++ b/.github/workflows/dependabot-deploy.yml
@@ -75,6 +75,10 @@ jobs:
         uses: actions/checkout@v4
         with:
           ref: main
+          # Need full history so the later "Sync main into staging" merge
+          # can find a common ancestor (otherwise: "refusing to merge
+          # unrelated histories").
+          fetch-depth: 0
 
       - name: Set up Node.js
         uses: actions/setup-node@v4