diff --git a/Gemfile b/Gemfile
index ca9f003..80076c6 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ gem 'rails', '~> 5.0.0', '>= 5.0.0.1'
 # Use mysql as the database for Active Record
 gem 'mysql2', '>= 0.3.18', '< 0.5'
 # Use Puma as the app server
-gem 'puma', '~> 3.0'
+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 cd6b82d..c7d0d66 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -83,7 +83,8 @@ GEM
     nio4r (2.1.0)
     nokogiri (1.8.1)
       mini_portile2 (~> 2.3.0)
-    puma (3.11.0)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-cors (1.0.2)
     rack-test (0.6.3)
@@ -169,7 +170,7 @@ DEPENDENCIES
   listen (~> 3.0.5)
   minitest (= 5.10.1)
   mysql2 (>= 0.3.18, < 0.5)
-  puma (~> 3.0)
+  puma (~> 4.3)
   rack-cors
   rails (~> 5.0.0, >= 5.0.0.1)
   sass-rails (~> 5.0)