diff --git a/ops/nixos/lib/switch-prebuilt.nix b/ops/nixos/lib/switch-prebuilt.nix
index 4adbb16a27..7820cb557d 100644
--- a/ops/nixos/lib/switch-prebuilt.nix
+++ b/ops/nixos/lib/switch-prebuilt.nix
@@ -10,8 +10,11 @@ pkgs.writeShellScriptBin "switch-prebuilt" ''
   export AWS_SECRET_ACCESS_KEY="${depot.ops.secrets.nixCache.AWS_SECRET_ACCESS_KEY}"
   system="''${1}"
 
-  # We should be a trusted-user.
-  nix copy -v --from 's3://lukegb-nix-cache?endpoint=storage.googleapis.com' --no-check-sigs "$system"
+  if [[ ! -e "$system" ]]; then
+    # We should be a trusted-user.
+    nix copy -v --from 's3://lukegb-nix-cache?endpoint=storage.googleapis.com' --no-check-sigs "$system"
+  fi
+
   diff "$system/etc/hostname" "/etc/hostname"
 
   # The next phase requires sudo, but it's harmless to run the preceding commands twice.