diff --git a/rails_5_test_app/Gemfile b/rails_5_test_app/Gemfile
index febf231..a46593f 100644
--- a/rails_5_test_app/Gemfile
+++ b/rails_5_test_app/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.3'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 4.3'
 # Use SCSS for stylesheets
 # gem 'sass-rails', '~> 5.0'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
diff --git a/rails_5_test_app/Gemfile.lock b/rails_5_test_app/Gemfile.lock
index 280816f..eddd77d 100644
--- a/rails_5_test_app/Gemfile.lock
+++ b/rails_5_test_app/Gemfile.lock
@@ -87,7 +87,8 @@ GEM
     nio4r (2.4.0)
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
-    puma (3.12.1)
+    puma (4.3.1)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -172,7 +173,7 @@ DEPENDENCIES
   byebug
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   rspec-rails (~> 3.8.2)
   spring