diff --git a/book/external/Nested-Books b/book/external/Nested-Books
index 94d5835..21c0a70 160000
--- a/book/external/Nested-Books
+++ b/book/external/Nested-Books
@@ -1 +1 @@
-Subproject commit 94d583570178ede097f8216b2aa06996d6e4b9ee
+Subproject commit 21c0a704f4b4a932e204991ddeb051f7487d9ac4