diff --git a/doc/set-up-gdk.md b/doc/set-up-gdk.md
index 37fd69f..8ef6f66 100644
--- a/doc/set-up-gdk.md
+++ b/doc/set-up-gdk.md
@@ -94,6 +94,10 @@ You can override the port used by this GDK with a 'port' file.
 
     echo 4000 > port
 
+Similarly, you can override the host (for example if you plan to use GDK inside a Docker container).
+
+    echo 0.0.0.0 > host
+
 If you want to work on GitLab CI you will need to install [GitLab Runner](https://gitlab.com/gitlab-org/gitlab-ci-multi-runner).
 
 To enable the OpenLDAP server, see the OpenLDAP instructions in this readme.