diff --git a/.github/workflows/backport.yml b/.github/workflows/backport.yml
index 5805401b08c7..ba5c06452664 100644
--- a/.github/workflows/backport.yml
+++ b/.github/workflows/backport.yml
@@ -39,6 +39,8 @@ jobs:
       - uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
         with:
           ref: ${{ github.event.pull_request.head.sha }}
+          # Avoid materializing full nixpkgs tree
+          sparse-checkout: .
           token: ${{ steps.app-token.outputs.token }}
           persist-credentials: true