diff --git a/Gemfile b/Gemfile
index eda3fad..5e830d6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.1.1'
 # 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 de8ce63..a8fb5c9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -199,7 +199,8 @@ GEM
       method_source (~> 0.8.1)
       slop (~> 3.4)
     public_suffix (2.0.5)
-    puma (3.9.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-contrib (1.2.0)
       rack (>= 0.9.1)
@@ -342,7 +343,7 @@ DEPENDENCIES
   mongoid
   mongoid-enum!
   mongoid_paranoia
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.1)
   rails-i18n (~> 5.0.0)
   rbnacl (< 5.0.0)