diff --git a/book/external/Nested-Books b/book/external/Nested-Books
index d659739..31b500d 160000
--- a/book/external/Nested-Books
+++ b/book/external/Nested-Books
@@ -1 +1 @@
-Subproject commit d659739766119a7065f8fe1424874ff935de14cb
+Subproject commit 31b500d8fafa88630095eb824fad2f89c8b9f04e