diff --git a/Gemfile b/Gemfile
index f54b20a..ad00dcf 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 bb0938c..74cb8e1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -134,7 +134,8 @@ GEM
     pg (1.1.4)
     popper_js (1.14.5)
     public_suffix (3.1.0)
-    puma (3.12.1)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -240,7 +241,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   offsite_payments!
   pg (>= 0.18, < 2.0)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   sass-rails (~> 5.0)
   selenium-webdriver