diff --git a/Gemfile b/Gemfile
index 71790fa..2339cb8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ end
 
 gem 'rails', '~> 5.1.4'
 gem 'pg', '~> 0.18'
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 4.3'
 gem 'sass-rails', '~> 5.0'
 gem 'uglifier', '>= 1.3.0'
 gem 'coffee-rails', '~> 4.2'
diff --git a/Gemfile.lock b/Gemfile.lock
index c15de9f..6e967e4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -140,7 +140,9 @@ 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 (2.4.0)
     minitest (5.11.3)
@@ -167,7 +169,8 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.2)
-    puma (3.11.3)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.4)
     rack-livereload (0.3.16)
       rack
@@ -294,7 +297,7 @@ DEPENDENCIES
   paperclip (~> 5.2.1)
   pg (~> 0.18)
   pry-rails
-  puma (~> 3.7)
+  puma (~> 4.3)
   rack-livereload
   rails (~> 5.1.4)
   rails_12factor