diff --git a/refume/Gemfile b/refume/Gemfile
index 93038f5..a4391c9 100644
--- a/refume/Gemfile
+++ b/refume/Gemfile
@@ -24,7 +24,7 @@ gem 'encryption'
 # Use sqlite3 as the database for Active Record
 #gem 'sqlite3'
 # 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/refume/Gemfile.lock b/refume/Gemfile.lock
index b8fe578..9503ce2 100644
--- a/refume/Gemfile.lock
+++ b/refume/Gemfile.lock
@@ -108,7 +108,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (1.2.2)
     public_suffix (4.0.3)
-    puma (3.12.4)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     pycall (1.3.0)
     rack (2.2.2)
     rack-proxy (0.6.5)
@@ -217,7 +218,7 @@ DEPENDENCIES
   jquery-rails (~> 4.3, >= 4.3.3)
   listen (>= 3.0.5, < 3.2)
   pg
-  puma (~> 3.7)
+  puma (~> 4.3)
   pycall
   rails (~> 5.1.6)
   rails-ujs (~> 0.1.0)