diff --git a/Gemfile b/Gemfile
index cf80388..d037492 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ end
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.1.4'
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 5.6', '>= 5.6.9'
 gem 'sass-rails', '~> 5.0'
 gem 'uglifier', '>= 1.3.0'
 gem 'coffee-rails', '~> 4.2'
diff --git a/Gemfile.lock b/Gemfile.lock
index b9d9f8d..30ce235 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -106,7 +106,8 @@ GEM
     nokogiri (1.8.1)
       mini_portile2 (~> 2.3.0)
     orm_adapter (0.5.0)
-    puma (3.11.2)
+    puma (5.6.9)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-test (0.8.2)
       rack (>= 1.0, < 3)
@@ -225,7 +226,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   listen (>= 3.0.5, < 3.2)
   mysql2 (< 0.5)
-  puma (~> 3.7)
+  puma (~> 5.6, >= 5.6.9)
   rails (~> 5.1.4)
   rails-assets-bootstrap!
   rails-assets-jquery!