diff --git a/Gemfile b/Gemfile
index a691701..dc45112 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,7 +7,7 @@ end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.1.4'
 # Use Puma as the app server
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 4.3'
 # Beautify
 gem 'htmlbeautifier'
 # bootstrap
diff --git a/Gemfile.lock b/Gemfile.lock
index adafd9e..b67e4e2 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -105,7 +105,8 @@ GEM
       mini_portile2 (~> 2.3.0)
     pg (0.21.0)
     public_suffix (3.0.1)
-    puma (3.11.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-test (0.8.2)
       rack (>= 1.0, < 3)
@@ -201,7 +202,7 @@ DEPENDENCIES
   masonry-rails
   metamagic
   pg
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.4)
   sass-rails (~> 5.0)
   selenium-webdriver