diff --git a/Gemfile b/Gemfile
index 7c06982..8f57e89 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ gem 'rails', '~> 5.2'
 # Use postgresql as the database for Active Record
 gem 'pg', '~> 1'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
diff --git a/Gemfile.lock b/Gemfile.lock
index 76dcfd5..2bcfee4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -11,8 +11,12 @@ GIT
       warden (~> 1.2.3)
 
 GEM
-  remote: https://rubygems.org/
   remote: https://rails-assets.org/
+  specs:
+    rails-assets-clipboard (2.0.4)
+
+GEM
+  remote: https://rubygems.org/
   specs:
     actioncable (5.2.4.5)
       actionpack (= 5.2.4.5)
@@ -221,7 +225,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (4.0.6)
-    puma (3.12.6)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     racc (1.5.2)
     rack (2.2.3)
     rack-livereload (0.3.17)
@@ -243,7 +248,6 @@ GEM
       bundler (>= 1.3.0)
       railties (= 5.2.4.5)
       sprockets-rails (>= 2.0.0)
-    rails-assets-clipboard (2.0.4)
     rails-controller-testing (1.0.4)
       actionpack (>= 5.0.1.x)
       actionview (>= 5.0.1.x)
@@ -403,7 +407,7 @@ DEPENDENCIES
   omniauth-github (~> 2)
   omniauth-rails_csrf_protection
   pg (~> 1)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rack-livereload (~> 0.3.16)
   rails (~> 5.2)
   rails-assets-clipboard!