diff --git a/Gemfile b/Gemfile
index 55f0110..bc80b9c 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,7 +12,7 @@ gem 'rails', '~> 5.1.1'
 # Use sqlite3 as the database for Active Record
 gem 'pg'
 # 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 61aa17b..3fc0198 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -111,7 +111,8 @@ GEM
       method_source (~> 0.8.1)
       slop (~> 3.4)
     public_suffix (2.0.5)
-    puma (3.9.1)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-proxy (0.6.2)
       rack
@@ -204,7 +205,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   pg
   pry
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.1)
   sass-rails (~> 5.0)
   selenium-webdriver