diff --git a/README.md b/README.md
index cceab08..ac901d9 100644
--- a/README.md
+++ b/README.md
@@ -11,6 +11,13 @@
 Docker deployment for [Drivers Hub: Backend](https://github.com/CharlesWithC/HubBackend).
 The deployment includes MariaDB, Valkey, and the banner generator.
 
+## Tested upstream version
+
+This deployment is tested with Drivers Hub: Backend
+[`v2.12.1`](https://github.com/CharlesWithC/HubBackend/releases/tag/v2.12.1).
+At the time of this test, the release tag and upstream `main` point to commit
+`a460eed`.
+
 ## Configure the deployment
 
 Get the backend source code. Then, create the deployment configuration and the