diff --git a/.github/workflows/build-then-cache.yaml b/.github/workflows/build-then-cache.yaml
index 40c85d5..28f4981 100644
--- a/.github/workflows/build-then-cache.yaml
+++ b/.github/workflows/build-then-cache.yaml
@@ -16,4 +16,6 @@ jobs:
           endpoint: ${{ secrets.ATTIC_ENDPOINT }}
           cache: ${{ secrets.ATTIC_CACHE }}
           token: ${{ secrets.ATTIC_TOKEN }}
+      # free useless disk space
+      - run: 'curl https://raw.githubusercontent.com/apache/arrow/31747f067a6ae29eca2d9bc68748500a8163d83e/ci/scripts/util_free_space.sh | bash'
       - run: 'nix build .#nixosConfigurations.nullbox.config.system.build.toplevel'