diff --git a/Gemfile b/Gemfile
index 58a56162..e036c3cf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,7 +14,7 @@ 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 78c8399c..3a1cbeff 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -125,7 +125,9 @@ GEM
     marcel (0.3.2)
       mimemagic (~> 0.3.2)
     method_source (0.9.0)
-    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)
@@ -157,7 +159,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (3.0.2)
-    puma (3.11.4)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-test (1.0.0)
       rack (>= 1.0, < 3)
@@ -267,7 +270,7 @@ DEPENDENCIES
   minitest-reporters
   prawn-rails
   prawn-table
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.0)
   rails-controller-testing
   sass-rails (~> 5.0)