diff --git a/Gemfile b/Gemfile
index 4f29b76..50ff3c1 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.2', '>= 5.2.2.1'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.3.6'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 4.3'
 gem 'rack-cors', require: 'rack/cors'
 gem 'jbuilder'
 gem 'rbnacl'
diff --git a/Gemfile.lock b/Gemfile.lock
index 0988062..e5d8946 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -104,7 +104,8 @@ GEM
     nokogiri (1.10.5)
       mini_portile2 (~> 2.4.0)
     public_suffix (4.0.1)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-cors (1.0.3)
     rack-proxy (0.6.5)
@@ -216,7 +217,7 @@ DEPENDENCIES
   jbuilder
   listen (>= 3.0.5, < 3.2)
   loofah (~> 2.3, >= 2.3.1)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rack-cors
   rack-reverse-proxy
   rails (~> 5.2.2, >= 5.2.2.1)