diff --git a/Gemfile b/Gemfile
index dc68a03..51fa34c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ gem 'rails', '~> 5.0.0'
 # Use sqlite3 as the database for Active Record
 # gem 'sqlite3','~> 1.3.6'
 # Use Puma as the app server
-gem 'puma', '~> 3.0'
+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 396bef1..836fb8a 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -86,7 +86,8 @@ GEM
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
-    puma (3.12.1)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -173,7 +174,7 @@ DEPENDENCIES
   jquery-rails
   listen (~> 3.0.5)
   pg
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.0)
   rails_12factor
   sass-rails (~> 5.0)