diff --git a/Gemfile b/Gemfile
index 7fd7f0e..0081a40 100644
--- a/Gemfile
+++ b/Gemfile
@@ -17,7 +17,7 @@ gem 'rails', '~> 5.2.3'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+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 90155db..97e6dfb 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -118,7 +118,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
     public_suffix (4.0.1)
-    puma (3.12.1)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rabl-rails (0.5.5)
       activesupport (>= 4.2)
       concurrent-ruby (~> 1.0, >= 1.0.2)
@@ -230,7 +231,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   milligram
   pg (>= 0.18, < 2.0)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rabl-rails
   rails (~> 5.2.3)
   redis (~> 4.0)