diff --git a/doc/.deploy_heroku/Gemfile.lock b/doc/.deploy_heroku/Gemfile.lock
index 25f3e44..450275a 100644
--- a/doc/.deploy_heroku/Gemfile.lock
+++ b/doc/.deploy_heroku/Gemfile.lock
@@ -1,7 +1,7 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    rack (1.5.2)
+    rack (1.6.13)
     rack-protection (1.5.1)
       rack
     sinatra (1.4.4)