diff --git a/docs/book.json b/docs/book.json
index f141a04..43e761a 100644
--- a/docs/book.json
+++ b/docs/book.json
@@ -20,7 +20,7 @@
           "text": "Master"
         },
         {
-          "value": "http://guide.opencord.org/400",
+          "value": "http://guide.opencord.org/cord-4.0",
           "text": "4.0"
         },
         {