diff --git a/Gemfile b/Gemfile
index a865f29..268ddac 100644
--- a/Gemfile
+++ b/Gemfile
@@ -58,7 +58,7 @@ gem "rvm-capistrano", group: :development, :require => false
 # gem 'bcrypt-ruby', '~> 3.0.0'
 
 # Use unicorn as the app server
-gem 'unicorn'
+gem 'unicorn', "5.5.1"
 
 gem "nokogiri"
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 2764868..85112d2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -194,7 +194,7 @@ DEPENDENCIES
   turbolinks
   twitter-bootstrap-rails
   uglifier (>= 1.3.0)
-  unicorn
+  unicorn (= 5.5.1)
 
 BUNDLED WITH
    1.16.4