diff --git a/examples/rails_4_button_example/Gemfile.lock b/examples/rails_4_button_example/Gemfile.lock
index 9597a9d..af8fe62 100644
--- a/examples/rails_4_button_example/Gemfile.lock
+++ b/examples/rails_4_button_example/Gemfile.lock
@@ -74,7 +74,7 @@ GEM
     multi_json (1.11.0)
     nokogiri (1.6.6.2)
       mini_portile (~> 0.6.0)
-    rack (1.6.0)
+    rack (1.6.12)
     rack-test (0.6.3)
       rack (>= 1.0)
     rails (4.2.1)