diff --git a/stacks/dev/docker-compose.yml b/stacks/dev/docker-compose.yml
index 8a1a7e9..acfbff2 100644
--- a/stacks/dev/docker-compose.yml
+++ b/stacks/dev/docker-compose.yml
@@ -57,6 +57,9 @@ services:
       - TZ
       - APP_URL=https://docs.ginnoir.com
       - APP_KEY
+      # stack.env leaks Plane's DATABASE_URL; Laravel prioritizes it over DB_* and
+      # would connect BookStack to postgres_plane. Pin it to BookStack's own MariaDB.
+      - DATABASE_URL=mysql://bookstack:bookstack_d3v_pass@mariadb_bookstack:3306/bookstack
       - DB_HOST=mariadb_bookstack
       - DB_PORT=3306
       - DB_USER=bookstack