diff --git a/Gemfile b/Gemfile
index 9209cb2..b7cb23f 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.4'
 # 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 1c2ac90..ea25957 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -114,7 +114,9 @@ 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 (0.1.4)
     mini_portile2 (2.3.0)
     minitest (5.10.3)
@@ -145,7 +147,8 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.0)
-    puma (3.10.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-test (0.7.0)
       rack (>= 1.0, < 3)
@@ -248,7 +251,7 @@ DEPENDENCIES
   pg (~> 0.18)
   pg_search
   pry-rails
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.4)
   rails_12factor
   sass-rails (~> 5.0)