diff --git a/Gemfile b/Gemfile
index ce11075..20a0c02 100644
--- a/Gemfile
+++ b/Gemfile
@@ -18,7 +18,7 @@ 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 2526ecc..8188e07 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -117,7 +117,9 @@ 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_magick (4.8.0)
     mini_mime (1.0.0)
     mini_portile2 (2.3.0)
@@ -129,7 +131,8 @@ GEM
       mini_portile2 (~> 2.3.0)
     orm_adapter (0.5.0)
     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)
@@ -239,7 +242,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   meta-tags
   mini_magick
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.0)
   rails-settings-cached
   sass-rails (~> 5.0)