diff --git a/Gemfile b/Gemfile
index 162301e..c351793 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ gem 'mini_magick',             '4.7.0'
 gem 'will_paginate',           '3.1.6'
 gem 'bootstrap-will_paginate', '1.0.0'
 gem 'bootstrap-sass',          '3.3.7'
-gem 'puma',                    '3.9.1'
+gem 'puma',                    '4.3.9'
 gem 'sass-rails',              '5.0.6'
 gem 'uglifier',                '3.2.0'
 gem 'coffee-rails',            '4.2.2'
diff --git a/Gemfile.lock b/Gemfile.lock
index e9c9260..095680c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -302,7 +302,8 @@ GEM
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    puma (3.9.1)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.0.6)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -424,7 +425,7 @@ DEPENDENCIES
   minitest-reporters (= 1.1.14)
   pg (= 0.20.0)
   pry
-  puma (= 3.9.1)
+  puma (= 4.3.9)
   rails (= 5.1.6)
   rails-controller-testing (= 1.0.2)
   sass-rails (= 5.0.6)