diff --git a/Gemfile b/Gemfile
index 617bc13..c259287 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,7 +12,7 @@ gem 'rails', '~> 5.1.5'
 # 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 8de4c0e..b5e8403 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -123,7 +123,8 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (4.0.5)
-    puma (3.12.6)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -235,7 +236,7 @@ DEPENDENCIES
   lazy_high_charts
   listen (>= 3.0.5, < 3.2)
   pry-rails
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.5)
   redcarpet
   rouge