diff --git a/Gemfile b/Gemfile
index 658b5c0..d34a109 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.3'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+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 d778acc..baef4a8 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,5 +1,4 @@
 GEM
-  remote: https://rubygems.org/
   remote: https://rails-assets.org/
   specs:
     actioncable (5.2.3)
@@ -182,7 +181,6 @@ GEM
     pg (1.1.4)
     popper_js (1.11.1)
     public_suffix (3.1.1)
-    puma (3.12.1)
     rack (2.0.7)
     rack-cors (1.1.0)
       rack (>= 2.0.0)
@@ -277,6 +275,12 @@ GEM
     xpath (3.2.0)
       nokogiri (~> 1.8)
 
+GEM
+  remote: https://rubygems.org/
+  specs:
+    puma (4.3.9)
+      nio4r (~> 2.0)
+
 PLATFORMS
   ruby
 
@@ -301,7 +305,7 @@ DEPENDENCIES
   mini_racer
   pg (>= 0.18, < 2.0)
   popper_js (~> 1.11.1)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rack-cors
   rails (~> 5.2.3)
   rails-assets-tether (>= 1.3.3)!