diff --git a/.gitea/workflows/check-flake.yaml b/.gitea/workflows/check-flake.yaml
index 318308e..5b1018f 100644
--- a/.gitea/workflows/check-flake.yaml
+++ b/.gitea/workflows/check-flake.yaml
@@ -26,9 +26,11 @@ jobs:
           export XDG_CONFIG_HOME="$(mktemp -d)"
           mkdir -p "$XDG_CONFIG_HOME/attic"
           attic login local "${{ vars.ATTIC_ENDPOINT }}" "${{ secrets.ATTIC_TOKEN }}"
-          # Get all system toplevel store paths
-          toplevels=$(nix eval .#nixosConfigurations --apply 'cs: map (n: "${cs.${n}.config.system.build.toplevel}") (builtins.attrNames cs)' --json | jq -r '.[]')
-          echo "Found $(echo "$toplevels" | wc -l) system toplevels"
+          # Get all system toplevel store paths, keeping only those valid in the local store
+          toplevels=$(nix eval .#nixosConfigurations --apply 'cs: map (n: "${cs.${n}.config.system.build.toplevel}") (builtins.attrNames cs)' --json \
+            | jq -r '.[]' \
+            | xargs -I{} sh -c 'nix path-info {} >/dev/null 2>&1 && echo {}')
+          echo "Found $(echo "$toplevels" | wc -l) valid system toplevels"
           # Expand to full closures, deduplicate, and filter out paths already
           # signed by cache.nixos.org — only our custom builds need caching
           paths=$(echo "$toplevels" \