diff --git a/Gemfile b/Gemfile
index 2ec349c..0482a25 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.0.7'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # 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 ba93994..af836f6 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -204,7 +204,8 @@ GEM
     pry (0.12.2)
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
-    puma (3.12.2)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.1.2)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -324,7 +325,7 @@ DEPENDENCIES
   omniauth-google-oauth2
   pg (>= 0.18, < 2.0)
   popper_js (~> 1.14.3)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.0.7)
   rails-assets-tether!
   ranked-model