diff --git a/Gemfile b/Gemfile
index b747855..8caccfa 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,7 +7,7 @@ gem 'rails', '~> 5.1', '>= 5.1.4'
 gem 'sqlite3', group: :development
 gem 'pg', '= 0.19.0', group: :production
 # 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 8fc0de8..fc2d8f1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -134,7 +134,8 @@ GEM
       ttfunk (~> 1.5)
     prawn-table (0.2.2)
       prawn (>= 1.3.0, < 3.0.0)
-    puma (3.11.2)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-protection (2.0.0)
       rack
@@ -284,7 +285,7 @@ DEPENDENCIES
   pg (= 0.19.0)
   prawn
   prawn-table
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.1, >= 5.1.4)
   rails_12factor
   rspec-rails (~> 3.5)