diff --git a/src/doc/book b/src/doc/book
index e6d6caab414..9bd223ca406 160000
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit e6d6caab41471f7115a621029bd428a812c5260e
+Subproject commit 9bd223ca406b1170a24942d6474f9e8a56f4a420