diff --git a/Gemfile b/Gemfile
index c37dbb0..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', '~> 3.12'
+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 6e3dda5..4f29b78 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -113,7 +113,8 @@ GEM
       method_source (~> 0.8.1)
       slop (~> 3.4)
     public_suffix (2.0.5)
-    puma (3.12.6)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-proxy (0.6.2)
       rack
@@ -206,7 +207,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   pg
   pry
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.1.1)
   sass-rails (~> 5.0)
   selenium-webdriver