diff --git a/Gemfile b/Gemfile
index 0b7a7d3..cbf3d02 100644
--- a/Gemfile
+++ b/Gemfile
@@ -6,7 +6,7 @@ gem 'rails', '~> 5.0.0', '>= 5.0.0.1'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3'
 # Use Puma as the app server
-gem 'puma', '~> 3.0'
+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 c10224c..ad2c6c1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -106,7 +106,8 @@ GEM
     nio4r (2.0.0)
     nokogiri (1.7.0.1)
       mini_portile2 (~> 2.1.0)
-    puma (3.7.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.1)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -199,7 +200,7 @@ DEPENDENCIES
   less-rails
   listen (~> 3.0.5)
   moving_average
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.0, >= 5.0.0.1)
   rails_real_favicon
   sqlite3