diff --git a/flipped-demos/ch04-rails/hw2-onramp/Gemfile b/flipped-demos/ch04-rails/hw2-onramp/Gemfile
index aad2026..9f14bc3 100644
--- a/flipped-demos/ch04-rails/hw2-onramp/Gemfile
+++ b/flipped-demos/ch04-rails/hw2-onramp/Gemfile
@@ -6,7 +6,7 @@ gem 'rails', '~> 4.2'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.0'
+gem 'puma', '~> 5.6'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
diff --git a/flipped-demos/ch04-rails/hw2-onramp/Gemfile.lock b/flipped-demos/ch04-rails/hw2-onramp/Gemfile.lock
index 6ed5dc0..9d5c3da 100644
--- a/flipped-demos/ch04-rails/hw2-onramp/Gemfile.lock
+++ b/flipped-demos/ch04-rails/hw2-onramp/Gemfile.lock
@@ -121,10 +121,12 @@ GEM
     minitest (5.11.3)
     multi_json (1.13.1)
     multi_test (0.1.2)
+    nio4r (2.5.9)
     nokogiri (1.10.1)
       mini_portile2 (~> 2.4.0)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (5.6.7)
+      nio4r (~> 2.0)
     rack (1.6.11)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -214,7 +216,7 @@ DEPENDENCIES
   jquery-rails
   launchy
   listen (~> 3.0.5)
-  puma (~> 3.0)
+  puma (~> 5.6)
   rails (~> 4.2)
   sass-rails (~> 5.0)
   spring