diff --git a/Gemfile b/Gemfile
index 3afde680..3f1c0742 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'bootstrap', '~> 4.3.1'
 gem 'coffee-rails', '4.2.2'
 gem 'jbuilder',     '2.7.0'
 gem 'jquery-rails', '4.3.1'
-gem 'puma',         '3.12.4'
+gem 'puma',         '4.3.9'
 gem 'rails',        '5.1.6'
 gem 'sass-rails',   '5.0.6'
 gem 'turbolinks',   '5.0.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index a71ad56a..9571eb2e 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -224,7 +224,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (4.0.3)
-    puma (3.12.4)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -383,7 +384,7 @@ DEPENDENCIES
   omniauth
   omniauth-twitter
   pg (= 0.20.0)
-  puma (= 3.12.4)
+  puma (= 4.3.9)
   rails (= 5.1.6)
   rails-controller-testing (= 1.0.2)
   rails_12factor