diff --git a/Gemfile b/Gemfile
index e4457ea..40784e2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,7 +13,7 @@ gem 'rails-erd'
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.0.7'
 # 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 d98d8c5..df44f06 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -90,7 +90,8 @@ GEM
       mini_portile2 (~> 2.3.0)
     pg (0.21.0)
     popper_js (1.14.3)
-    puma (3.12.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -183,7 +184,7 @@ DEPENDENCIES
   jquery-rails
   listen (~> 3.0.5)
   pg (~> 0.18)
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.7)
   rails-erd
   sass-rails (~> 5.0)