diff --git a/README.md b/README.md
index 9fd908b..1760fba 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,7 @@ Allowlist of npubs is set via `NOSTR_ALLOWED_NPUBS`. Anything else is rejected b
      docker inspect -f '{{range $name, $_ := .NetworkSettings.Networks}}{{$name}}{{"\n"}}{{end}}' datum_datum_1
      ```
    - On Umbrel this is usually `umbrel_main_network`, which is the compose default.
-   - Leave `DATUM_URL` unset unless you need to override it. The default is `http://datum_datum_1:21000`, which avoids Umbrel's host proxy and stale container IPs.
+   - Leave `DATUM_URL` unset unless you need to override it. The default is `http://datum:21000`, which uses Datum's Compose service alias and avoids Umbrel's host proxy and stale container IPs.
 
 4. Open the dashboard, log in with one of the allowed npubs, watch your boards lose at hashing in style.
 
diff --git a/docker-compose.yml b/docker-compose.yml
index f7f99a9..70c9ff4 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -25,7 +25,7 @@ services:
       CORS_ORIGIN: "${CORS_ORIGIN:-}"
       # Reach the Datum gateway container directly on its Docker network.
       # Do not use the Umbrel host proxy here; it serves the Umbrel web shell.
-      DATUM_URL: "${DATUM_URL:-http://datum_datum_1:21000}"
+      DATUM_URL: "${DATUM_URL:-http://datum:21000}"
       DATUM_ADMIN_USER: "${DATUM_ADMIN_USER:-admin}"
       DATUM_ADMIN_PASSWORD: "${DATUM_ADMIN_PASSWORD?must be set}"
       DATUM_POLL_INTERVAL_MS: "${DATUM_POLL_INTERVAL_MS:-5000}"