diff --git a/docker/docker-compose.yml b/docker/docker-compose.yml
index c3efd687b65..2eca99b5ab3 100644
--- a/docker/docker-compose.yml
+++ b/docker/docker-compose.yml
@@ -197,6 +197,7 @@ services:
       - log_min_messages=fatal # prevents Realtime polling queries from appearing in logs
     restart: unless-stopped
     ports:
+      # Pass down internal port because it's set dynamically by other services
       - ${POSTGRES_PORT}:${POSTGRES_PORT}
     environment:
       POSTGRES_HOST: /var/run/postgresql