diff --git a/README.md b/README.md
index a1ed3fa1..22c10054 100644
--- a/README.md
+++ b/README.md
@@ -15,6 +15,17 @@ This is a [Node.js](https://nodejs.org/en/) module available through the
 $ npm install express-session
 ```
 
+## Debugging
+
+```sh
+$ set DEBUG=express-session
+```
+
+Setting this property prior to the run (use `export` in UNIX)
+enables [`debug`](https://www.npmjs.com/package/debug) mode,
+and prints minimal but vital debug information pertinent
+to the life cycle of the session.
+
 ## API
 
 ```js