diff --git a/docker-compose.yml b/docker-compose.yml
index 2f964e241e58e8acc6beae71d908783ed86d3567..db00f3cd75941b64a871147860b7a9c92ac58d01 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -32,6 +32,7 @@ services:
   pma:
     image: phpmyadmin/phpmyadmin
     environment:
+      # https://docs.phpmyadmin.net/en/latest/setup.html#docker-environment-variables
       PMA_HOST: db
       PMA_PORT: 3306
       MYSQL_ROOT_PASSWORD: "${DB_ROOT_PASSWORD}"