diff --git a/Gemfile b/Gemfile
index aad9794..2524f7f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,7 +12,7 @@ gem 'kaminari'
 # Use postgresql as the database for Active Record
 gem 'pg', '~> 0.18'
 # 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 e94191d..2761ef1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -127,7 +127,9 @@ 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 (5.10.3)
@@ -148,7 +150,8 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.1)
-    puma (3.11.0)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-test (0.8.2)
       rack (>= 1.0, < 3)
@@ -245,7 +248,7 @@ DEPENDENCIES
   paperclip
   pg (~> 0.18)
   pry-rails
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.4)
   sass-rails (~> 5.0)
   selenium-webdriver