diff --git a/book/Gemfile.lock b/book/Gemfile.lock
index 82085fc..d4ccb7a 100644
--- a/book/Gemfile.lock
+++ b/book/Gemfile.lock
@@ -189,7 +189,7 @@ GEM
     thor (0.19.1)
     thread_safe (0.3.6)
     tilt (1.4.1)
-    tzinfo (1.2.5)
+    tzinfo (1.2.10)
       thread_safe (~> 0.1)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)