diff --git a/Gemfile b/Gemfile
index 98a406d..c2db45c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,7 +13,7 @@ gem 'rails', '~> 5.1.4'
 # 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/Gemfile.lock b/Gemfile.lock
index 0ff3d58..d793491 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -95,7 +95,8 @@ GEM
       mini_portile2 (~> 2.8.0)
       racc (~> 1.4)
     public_suffix (3.0.1)
-    puma (3.11.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     racc (1.6.0)
     rack (2.0.3)
     rack-test (0.8.2)
@@ -181,7 +182,7 @@ DEPENDENCIES
   coffee-rails (~> 4.2)
   jbuilder (~> 2.5)
   mini_magick
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.4)
   sass-rails (~> 5.0)
   selenium-webdriver