diff --git a/Gemfile b/Gemfile
index b6fbb02..78881f2 100644
--- a/Gemfile
+++ b/Gemfile
@@ -34,7 +34,7 @@ gem 'rails', '~> 5.2.3'
 # Use sqlite3 as the database for Active Record
 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 35041df..1ff694d 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -183,7 +183,8 @@ GEM
     orm_adapter (0.5.0)
     popper_js (1.14.5)
     public_suffix (3.1.1)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -314,7 +315,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   jquery-rails
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   roo (~> 2.8, >= 2.8.2)
   roo-xls