diff --git a/caldecott_helper/Gemfile b/caldecott_helper/Gemfile
index ccabb3d..952da60 100644
--- a/caldecott_helper/Gemfile
+++ b/caldecott_helper/Gemfile
@@ -1,6 +1,6 @@
 source "http://rubygems.org"
 
-gem 'rack', '~> 1.2.0'
+gem 'rack', '~> 2.1.4'
 gem 'caldecott', '= 0.0.3'
 gem 'bundler'
 gem 'em-websocket'
diff --git a/caldecott_helper/Gemfile.lock b/caldecott_helper/Gemfile.lock
index 4d6c777..daa8dc6 100644
--- a/caldecott_helper/Gemfile.lock
+++ b/caldecott_helper/Gemfile.lock
@@ -23,15 +23,22 @@ GEM
     escape_utils (0.2.4)
     eventmachine (0.12.10)
     json (1.6.1)
-    rack (1.2.4)
-    sinatra (1.2.7)
-      rack (~> 1.1)
-      tilt (>= 1.2.2, < 2.0)
+    mustermann (1.1.1)
+      ruby2_keywords (~> 0.0.1)
+    rack (2.1.4)
+    rack-protection (2.0.8.1)
+      rack
+    ruby2_keywords (0.0.2)
+    sinatra (2.0.8.1)
+      mustermann (~> 1.0)
+      rack (~> 2.0)
+      rack-protection (= 2.0.8.1)
+      tilt (~> 2.0)
     thin (1.2.11)
       daemons (>= 1.0.9)
       eventmachine (>= 0.12.6)
       rack (>= 1.0.0)
-    tilt (1.3.3)
+    tilt (2.0.10)
     uuidtools (2.1.2)
 
 PLATFORMS
@@ -43,6 +50,6 @@ DEPENDENCIES
   caldecott (= 0.0.3)
   em-websocket
   json
-  rack (~> 1.2.0)
+  rack (~> 2.1.4)
   thin
   uuidtools