diff --git a/src/doc/book b/src/doc/book
index cff0930664b..fa91738b663 160000
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit cff0930664b688f1dd22aefb3d16944eb4cdbfd5
+Subproject commit fa91738b66367b6f70b078251868a071f1991ace