diff --git a/Gemfile b/Gemfile
index 26e7098..9ba2f30 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.6'
 # Use sqlite3 as the database for Active Record
 
 # 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 df1e4c5..412f8c9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -107,7 +107,8 @@ GEM
     pg (0.21.0)
     popper_js (1.14.3)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.5)
     rack-attack (5.4.2)
       rack (>= 1.0, < 3)
@@ -208,7 +209,7 @@ DEPENDENCIES
   jquery-rails
   listen (>= 3.0.5, < 3.2)
   pg
-  puma (~> 3.7)
+  puma (~> 4.3)
   rack-attack (~> 5.4.2)
   rails (~> 5.1.6)
   redis (~> 4.0)