diff --git a/Gemfile b/Gemfile
index cd9d239..e1a9281 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.6'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.7'
+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 8dd6112..9ae763f 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -87,7 +87,8 @@ GEM
       mini_portile2 (~> 2.3.0)
     orm_adapter (0.5.0)
     pg (1.0.0)
-    puma (3.11.4)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-test (1.0.0)
       rack (>= 1.0, < 3)
@@ -176,7 +177,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   pg (>= 0.18, < 2.0)
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.6)
   sass-rails (~> 5.0)
   spring