diff --git a/Gemfile b/Gemfile
index d217f6f..b301aa0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ gem 'rails', '~> 5.0.0', '>= 5.0.0.1'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # 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 43fa837..bd045f7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -84,7 +84,8 @@ GEM
       mini_portile2 (~> 2.3.0)
     nokogiri (1.8.2-x86-mingw32)
       mini_portile2 (~> 2.3.0)
-    puma (3.11.3)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.4)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -167,7 +168,7 @@ DEPENDENCIES
   coffee-rails (~> 4.2)
   jbuilder (~> 2.5)
   jquery-rails
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.0, >= 5.0.0.1)
   sass-rails (~> 5.0)
   sqlite3