diff --git a/Gemfile b/Gemfile
index 1b3da26..adde090 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.0'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+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 02e4451..d5ca7f7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -118,7 +118,9 @@ GEM
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
-    mimemagic (0.3.2)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.0)
     mini_portile2 (2.3.0)
     minitest (5.11.3)
@@ -129,7 +131,8 @@ GEM
     nokogiri (1.8.2)
       mini_portile2 (~> 2.3.0)
     public_suffix (3.0.2)
-    puma (3.11.3)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.4)
     rack-test (1.0.0)
       rack (>= 1.0, < 3)
@@ -260,7 +263,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   jquery-rails
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.0)
   rails-controller-testing
   rails-settings-cached