diff --git a/Gemfile b/Gemfile
index 78f7a95..01fd200 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.0.2'
 # Use sqlite3 as the database for Active Record
 
 # 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 6e35202..3c198e3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -102,7 +102,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     orm_adapter (0.5.0)
     pg (0.18.4)
-    puma (3.12.6)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -199,7 +200,7 @@ DEPENDENCIES
   jquery-rails
   listen (~> 3.0.5)
   pg (= 0.18.4)
-  puma (~> 3.0)
+  puma (~> 4.3)
   rails (~> 5.0.2)
   sass-rails (~> 5.0)
   simple_form (~> 3.2, >= 3.2.1)