diff --git a/external/book b/external/book
index db95d22564bd94d4beaf4439f7c9b456e7510c6b..0aa844b15af5f09d1f7c9effa60ea0da1cd0c84f 160000
--- a/external/book
+++ b/external/book
@@ -1 +1 @@
-Subproject commit db95d22564bd94d4beaf4439f7c9b456e7510c6b
+Subproject commit 0aa844b15af5f09d1f7c9effa60ea0da1cd0c84f