diff --git a/Gemfile b/Gemfile
index f40733e..165ba2b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,7 +12,7 @@ gem 'rails', '~> 5.0.1'
 # Use sqlite3 as the database for Active Record
 # gem 'sqlite3'
 # 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 59bf04d..7f70141 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -135,7 +135,8 @@ GEM
     pg (0.20.0)
     popper_js (1.14.7)
     public_suffix (4.0.3)
-    puma (3.12.4)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.2.2)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -261,7 +262,7 @@ DEPENDENCIES
   paperclip (~> 5.2.0)
   pg (= 0.20.0)
   popper_js (~> 1.14.5)
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.1)
   rails-assets-tether (>= 1.1.0)
   rails-controller-testing