diff --git a/Gemfile b/Gemfile
index 499151c..6002a2b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rubocop', require: false
 gem 'haml-rails', '~> 1.0'
 gem 'rails', '~> 5.1.5'
 gem 'mysql2', '>= 0.3.18', '< 0.5'
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 4.3'
 gem 'sass-rails', '~> 5.0'
 gem 'uglifier', '>= 1.3.0'
 gem 'pry-rails'
diff --git a/Gemfile.lock b/Gemfile.lock
index d43d51a..86ab93a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -142,7 +142,8 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.2)
-    puma (3.11.4)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-proxy (0.6.5)
       rack
@@ -280,7 +281,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   mysql2 (>= 0.3.18, < 0.5)
   pry-rails
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.5)
   rails-controller-testing
   rspec-rails (~> 3.7)