diff --git a/Gemfile b/Gemfile
index d332007..1f03245 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.4'
 # Use sqlite3 as the database for Active Record
 gem 'mysql2'
 # 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 2899fa5..7065634 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -142,7 +142,8 @@ GEM
     polyamorous (1.3.3)
       activerecord (>= 3.0)
     public_suffix (3.0.2)
-    puma (3.11.3)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.4)
     rack-test (0.8.3)
       rack (>= 1.0, < 3)
@@ -245,7 +246,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   mysql2
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.4)
   sass-rails (~> 5.0)
   selenium-webdriver