diff --git a/docker-compose.yml b/docker-compose.yml
index b8746ec..f150f38 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -11,7 +11,13 @@ services:
     environment:
       - CADDY_HOSTNAME=${CADDY_HOSTNAME}
       - ACME_EMAIL=${ACME_EMAIL}
-      - VULTR_API_KEY=${VULTR_API_KEY:?VULTR_API_KEY must be exported in your shell}
+      # Optional: only required for Caddy's DNS-01 cert renewal via Vultr's
+      # API. Cert is valid ~90 days; this env var only matters within the
+      # final 30d renewal window. Empty default keeps `docker compose up`
+      # working without the key in scope. Set it when renewal is imminent,
+      # OR migrate Caddy to caddy-dns/rfc2136 (via our plugin) and retire
+      # the Vultr dependency entirely.
+      - VULTR_API_KEY=${VULTR_API_KEY:-}
     volumes:
       - ./caddy/Caddyfile:/etc/caddy/Caddyfile:ro
       - ./caddy-data:/data