diff --git a/external/book b/external/book
index b030b6c9220e6e95f934d481470490ae994d4746..ffcf5e451e3830dfec33061295f8705c4bc43a9d 160000
--- a/external/book
+++ b/external/book
@@ -1 +1 @@
-Subproject commit b030b6c9220e6e95f934d481470490ae994d4746
+Subproject commit ffcf5e451e3830dfec33061295f8705c4bc43a9d