diff --git a/Gemfile b/Gemfile
index c4307a0..577990a 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'jbuilder', '~> 2.0'
 gem 'jquery-rails'
 gem 'mailboxer'
 gem 'pg', '~> 0.15'
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 4.3'
 gem 'rake', '~> 11.1', '>= 11.1.2'
 gem 'sass-rails', '~> 5.0'
 gem 'turbolinks'
diff --git a/Gemfile.lock b/Gemfile.lock
index f933d25..78c0379 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -132,7 +132,9 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (1.0.0)
-    mimemagic (0.3.5)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_magick (4.10.1)
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
@@ -149,7 +151,8 @@ GEM
       byebug (~> 11.0)
       pry (~> 0.13.0)
     public_suffix (4.0.5)
-    puma (3.12.6)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -287,7 +290,7 @@ DEPENDENCIES
   mailboxer
   pg (~> 0.15)
   pry-byebug
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails-html-sanitizer (~> 1.0.4)
   rails_12factor
   rake (~> 11.1, >= 11.1.2)