diff --git a/Gemfile b/Gemfile
index afd918b..f9c6e4a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.7'
 # Use mysql as the database for Active Record
 gem 'mysql2', '>= 0.3.18', '< 0.6.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index df69465..cf40c7d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -105,7 +105,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     popper_js (1.16.0)
     public_suffix (4.0.4)
-    puma (3.12.6)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -214,7 +215,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   jquery-rails
   mysql2 (>= 0.3.18, < 0.6.0)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.1.7)
   sass-rails (~> 5.0)
   selenium-webdriver