diff --git a/Gemfile b/Gemfile
index e19f300..9998210 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.3'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+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 ab95151..82e8b1b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -88,7 +88,8 @@ GEM
     nokogiri (1.10.8)
       mini_portile2 (~> 2.4.0)
     public_suffix (3.1.0)
-    puma (3.12.6)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -177,7 +178,7 @@ DEPENDENCIES
   coffee-rails (~> 4.2)
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.1.3)
   sass-rails (~> 5.0)
   selenium-webdriver