diff --git a/Gemfile b/Gemfile
index 2082b93..c37c6fd 100644
--- a/Gemfile
+++ b/Gemfile
@@ -9,7 +9,7 @@ end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.1.2'
 # Use Puma as the app server
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 4.3'
 # Convert bootstrap's native less scc to sass
 gem 'bootstrap-sass', '3.3.7'
 # Use SCSS for stylesheets
diff --git a/Gemfile.lock b/Gemfile.lock
index 760f0d3..a68e634 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -132,7 +132,8 @@ GEM
       coderay (~> 1.1.0)
       method_source (~> 0.9.0)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -236,7 +237,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   minitest-reporters (= 1.1.14)
   pg (= 0.18.4)
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.2)
   rails-controller-testing
   sass-rails (~> 5.0)