diff --git a/Gemfile b/Gemfile
index ba8c2cf..428518e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.7'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.7'
+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 f6248d3..cf5f0bc 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -170,7 +170,8 @@ GEM
       coderay (~> 1.1)
       method_source (~> 1.0)
     public_suffix (4.0.5)
-    puma (3.12.6)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     pusher-client (0.6.2)
       json
       websocket (~> 1.0)
@@ -351,7 +352,7 @@ DEPENDENCIES
   orderly
   pg (>= 0.18, < 2.0)
   pry
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.7)
   rspec-rails
   rubocop-rails