diff --git a/book/en/src/preface.md b/book/en/src/preface.md
index 15aaea5ce7..1728062b67 100644
--- a/book/en/src/preface.md
+++ b/book/en/src/preface.md
@@ -11,7 +11,10 @@ There is a translation of this book in [Russian].
 
 [Russian]: ../ru/index.html
 
-**HEADS UP** This is an **alpha** pre-release; there may be breaking changes in
+This is the documentation of v0.5.x of RTFM; for the documentation of version
+v0.4.x go [here](../../0.4/book/en).
+
+**HEADS UP** This is a **beta** pre-release; there may be breaking changes in
 the API and semantics before a proper release is made.
 
 {{#include ../../../README.md:5:44}}