diff --git a/chapter_01/Gemfile.lock b/chapter_01/Gemfile.lock
index 99375d3..c357ff1 100644
--- a/chapter_01/Gemfile.lock
+++ b/chapter_01/Gemfile.lock
@@ -14,9 +14,11 @@ GEM
       multi_json (~> 1.0)
     arel (3.0.2)
     builder (3.0.0)
+    concurrent-ruby (1.1.10)
     diff-lcs (1.1.3)
     ffi (1.0.11)
-    i18n (0.6.0)
+    i18n (0.9.5)
+      concurrent-ruby (~> 1.0)
     json (1.7.3)
     mime-types (1.19)
     multi_json (1.3.6)