diff --git a/hello_app/Gemfile b/hello_app/Gemfile
index 8a86b27..0683837 100644
--- a/hello_app/Gemfile
+++ b/hello_app/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.6'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # 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/hello_app/Gemfile.lock b/hello_app/Gemfile.lock
index 5357939..0e0ba57 100644
--- a/hello_app/Gemfile.lock
+++ b/hello_app/Gemfile.lock
@@ -88,7 +88,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (0.20.0)
     public_suffix (4.0.1)
-    puma (3.12.2)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -178,7 +179,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   pg (= 0.20.0)
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.6)
   sass-rails (~> 5.0)
   selenium-webdriver