diff --git a/Gemfile.lock b/Gemfile.lock
index 77241ae..8fe1bd2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -60,6 +60,7 @@ GEM
       coffee-script-source
       execjs
     coffee-script-source (1.9.1.1)
+    concurrent-ruby (1.1.6)
     cucumber (1.3.19)
       builder (>= 2.1.2)
       diff-lcs (>= 1.1.3)
@@ -119,7 +120,7 @@ GEM
       mini_portile (~> 0.6.0)
     quiet_assets (1.1.0)
       railties (>= 3.1, < 5.0)
-    rack (1.5.2)
+    rack (1.5.5)
     rack-contrib (1.2.0)
       rack (>= 0.9.1)
     rack-test (0.6.3)
@@ -165,8 +166,9 @@ GEM
     simplecov-html (0.8.0)
     single_test (0.6.0)
       rake
-    sprockets (3.0.3)
-      rack (~> 1.0)
+    sprockets (3.7.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
     sprockets-rails (2.2.4)
       actionpack (>= 3.0)
       activesupport (>= 3.0)