diff --git a/Gemfile b/Gemfile
index 2e832e6e4..ab024dc53 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@
 gem 'eventmachine'
 gem 'thin'
 gem 'sinatra'
-gem 'rack'
+gem 'rack', '~> 1.6.5'
 gem 'em-websocket' # WebSocket support
 gem 'uglifier'
 gem 'mime-types'
diff --git a/Gemfile.lock b/Gemfile.lock
index 6c73a2a01..0bdcec972 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -52,7 +52,6 @@ GEM
       rex
     msgpack (1.1.0)
     multi_json (1.12.1)
-    mustermann (1.0.0)
     nokogiri (1.7.2)
       mini_portile2 (~> 2.1.0)
     parseconfig (1.0.8)
@@ -60,8 +59,8 @@ GEM
     qr4r (0.4.1)
       mojo_magick
       rqrcode
-    rack (2.0.3)
-    rack-protection (2.0.0)
+    rack (1.6.8)
+    rack-protection (1.5.3)
       rack
     rainbow (2.2.2)
       rake
@@ -85,11 +84,10 @@ GEM
       eventmachine (~> 1.0.0)
       rexec (~> 1.6.2)
     rubyzip (1.2.1)
-    sinatra (2.0.0)
-      mustermann (~> 1.0)
-      rack (~> 2.0)
-      rack-protection (= 2.0.0)
-      tilt (~> 2.0)
+    sinatra (1.4.8)
+      rack (~> 1.5)
+      rack-protection (~> 1.4)
+      tilt (>= 1.3, < 3)
     term-ansicolor (1.6.0)
       tins (~> 1.0)
     thin (1.7.1)
@@ -97,7 +95,7 @@ GEM
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)
     tilt (2.0.7)
-    tins (1.14.0)
+    tins (1.15.0)
     uglifier (3.2.0)
       execjs (>= 0.3.0, < 3)
 
@@ -123,7 +121,7 @@ DEPENDENCIES
   nokogiri (~> 1.7.1)
   parseconfig
   qr4r
-  rack
+  rack (~> 1.6.5)
   rubydns (~> 0.7.3)
   rubyzip (~> 1.2.1)
   sinatra