diff --git a/Gemfile b/Gemfile
index 549e290..cbe8199 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,7 +13,7 @@ gem 'pg', '~> 0.18.4'
 gem 'sqlite3'
 
 # 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 a0fd31b..1dfb855 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -141,7 +141,8 @@ GEM
       ttfunk
     pg (0.18.4)
     public_suffix (4.0.1)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-cors (1.0.3)
     rack-test (1.1.0)
@@ -276,7 +277,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   pdf-reader
   pg (~> 0.18.4)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rack-cors
   rails (~> 5.2.3)
   rspec-rails