diff --git a/Gemfile b/Gemfile
index 8e4729fc7..0d202f18f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ gem 'httpclient', '~> 2.4.0'
 gem 'nokogiri', '~> 1.6.3.1'
 gem 'git', '~> 1.2.8'
 gem 'parallel', '~> 1.2.4'
-gem 'puma', '~> 2.9.0'
+gem 'puma', '~> 4.3.9'
 gem 'sinatra', '~> 1.4.5'
 gem 'sinatra-contrib', '~> 1.4.2'
 gem 'i18n', '~> 0.7.0'
diff --git a/Gemfile.lock b/Gemfile.lock
index 838a9cf13..fff449368 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -11,14 +11,15 @@ GEM
     mini_portile (0.6.0)
     multi_json (1.10.1)
     multipart-post (2.0.0)
+    nio4r (2.5.8)
     nokogiri (1.6.3.1)
       mini_portile (= 0.6.0)
     octokit (3.3.1)
       sawyer (~> 0.5.3)
     parallel (1.2.4)
-    puma (2.9.0)
-      rack (>= 1.1, < 2.0)
-    rack (1.5.2)
+    puma (4.3.9)
+      nio4r (~> 2.0)
+    rack (1.6.13)
     rack-protection (1.5.3)
       rack
     rack-test (0.6.2)
@@ -50,6 +51,6 @@ DEPENDENCIES
   nokogiri (~> 1.6.3.1)
   octokit (~> 3.3.1)
   parallel (~> 1.2.4)
-  puma (~> 2.9.0)
+  puma (~> 4.3.9)
   sinatra (~> 1.4.5)
   sinatra-contrib (~> 1.4.2)