diff --git a/Gemfile b/Gemfile
index b8cf4a7..67dfad3 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.2'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+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 fbb9e20..a975595 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -135,7 +135,8 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.6)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -205,7 +206,6 @@ GEM
       tzinfo (>= 1.0.0)
     uglifier (4.1.20)
       execjs (>= 0.3.0, < 3)
-    wdm (0.1.1)
     web-console (3.7.0)
       actionview (>= 5.0)
       activemodel (>= 5.0)
@@ -236,7 +236,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   pg (>= 0.18, < 2.0)
   pry-rails
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.2)
   sass-rails (~> 5.0)
   selenium-webdriver
@@ -244,7 +244,6 @@ DEPENDENCIES
   spring-watcher-listen (~> 2.0.0)
   tzinfo-data
   uglifier (>= 1.3.0)
-  wdm (>= 0.1.0)
   web-console (>= 3.3.0)
 
 RUBY VERSION