diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 96be0f1795..d135309de2 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -12,6 +12,8 @@ nixCache:
   script:
     - "nix run -f ./ third_party.nixpkgs.bash -c ./hack/populate_secrets.sh"
     - "nix build -v -f ./ci-root.nix --substituters \"https://cache.nixos.org/ s3://lukegb-nix-cache?endpoint=storage.googleapis.com&trusted=1\""
+    - "rm /nix/var/nix/gcroots/per-user/$USER/last-built-systems || true"
+    - "cp ./result /nix/var/nix/gcroots/per-user/$USER/last-built-systems"
     - "nix copy -v --to 's3://lukegb-nix-cache?endpoint=storage.googleapis.com' ./result"
   tags:
     - cacher