diff --git a/nixos-module.nix b/nixos-module.nix
index 4f190f41e4..b16eafdb79 100644
--- a/nixos-module.nix
+++ b/nixos-module.nix
@@ -63,6 +63,9 @@ in
           "PORT=${toString cfg.port}"
           # Agents are managed at runtime via the admin API and persisted here.
           "AGENTS_FILE=/var/lib/n8n-openai/agents.json"
+          # Elixir release needs a cookie; the release's start script reads
+          # releases/COOKIE which isn't baked in, so set it explicitly.
+          "RELEASE_COOKIE=n8n-openai-adapter"
         ];
         Restart = "always";
         RestartSec = 5;