diff --git a/Gemfile b/Gemfile
index c810229..f8fe7da 100644
--- a/Gemfile
+++ b/Gemfile
@@ -23,7 +23,7 @@ gem 'rails', '~> 5.1.6', '>= 5.1.6.1'
 
 
 # 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 bbce738..6cfe984 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -175,7 +175,8 @@ GEM
     pg (1.1.4)
     populator (1.0.0)
     public_suffix (3.1.1)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.1.1)
     rack-contrib (2.1.0)
       rack (~> 2.0)
@@ -317,7 +318,7 @@ DEPENDENCIES
   morrisjs-rails
   pg
   populator (= 1.0.0)
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.6, >= 5.1.6.1)
   rails-controller-testing (= 1.0.2)
   raphael-rails