diff --git a/Gemfile b/Gemfile
index bccab3d..6e2b494 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,7 @@ source 'https://rubygems.org'
 ruby '2.4.1'
 
 # HTTP server for Ruby/Rack recommended by Heroku
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 3.12'
 
 # Middleman
 gem 'middleman', '~> 4.2', '>= 4.2.1'
diff --git a/Gemfile.lock b/Gemfile.lock
index fd288f2..cb5f643 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -90,7 +90,7 @@ GEM
       activesupport (>= 3.1)
     parallel (1.12.0)
     public_suffix (3.0.0)
-    puma (3.11.2)
+    puma (3.12.4)
     rack (2.0.3)
     rack-contrib (2.0.1)
       rack (~> 2.0)
@@ -121,7 +121,7 @@ DEPENDENCIES
   itcsscli (~> 0.1.15)
   middleman (~> 4.2, >= 4.2.1)
   middleman-livereload (~> 3.4, >= 3.4.6)
-  puma (~> 3.11)
+  puma (~> 3.12)
   rack-contrib (~> 2.0)
   slim (~> 3.0, >= 3.0.8)
   tzinfo-data