diff --git a/Rails/Chatroom/Gemfile b/Rails/Chatroom/Gemfile
index 2685015..e532b26 100644
--- a/Rails/Chatroom/Gemfile
+++ b/Rails/Chatroom/Gemfile
@@ -13,7 +13,7 @@ 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', '~> 3.12'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
diff --git a/Rails/Chatroom/Gemfile.lock b/Rails/Chatroom/Gemfile.lock
index 2d038c4..f200998 100644
--- a/Rails/Chatroom/Gemfile.lock
+++ b/Rails/Chatroom/Gemfile.lock
@@ -91,7 +91,7 @@ GEM
     nokogiri (1.8.2)
       mini_portile2 (~> 2.3.0)
     popper_js (1.12.9)
-    puma (3.11.4)
+    puma (3.12.4)
     rack (2.0.4)
     rack-test (1.0.0)
       rack (>= 1.0, < 3)
@@ -177,7 +177,7 @@ DEPENDENCIES
   jquery-rails
   js_cookie_rails
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.7)
+  puma (~> 3.12)
   rails (~> 5.1.6)
   sass-rails (~> 5.0)
   spring