diff --git a/Gemfile b/Gemfile
index 6cef74f..6aefba4 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,6 +9,6 @@ end
 # for running rake assets:server
 group :server do
   gem "unified-assets", "0.0.1"
-  gem "rack",           "1.5.2"
+  gem "rack",           "2.1.4"
   gem "thin",           "1.5.0"
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index e0d8cbc..c2682da 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,7 +4,7 @@ GEM
     chunky_png (1.2.1)
     daemons (1.1.9)
     eventmachine (1.0.0)
-    rack (1.5.2)
+    rack (2.1.4)
     sprite-factory (1.4.1)
     thin (1.5.0)
       daemons (>= 1.0.9)
@@ -18,7 +18,7 @@ PLATFORMS
 
 DEPENDENCIES
   chunky_png (= 1.2.1)
-  rack (= 1.5.2)
+  rack (= 2.1.4)
   sprite-factory (= 1.4.1)
   thin (= 1.5.0)
   unified-assets (= 0.0.1)