diff --git a/viewer/Gemfile b/viewer/Gemfile
index eca1f90..30a2faf 100644
--- a/viewer/Gemfile
+++ b/viewer/Gemfile
@@ -5,7 +5,7 @@ ruby '>= 2.6.5'
 
 gem 'rails', '~> 5.2.4'
 gem 'pg', '>= 0.18', '< 2.0'
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 4.3'
 gem 'tzinfo-data'
 gem 'dotenv-rails'
 gem 'blazer'
diff --git a/viewer/Gemfile.lock b/viewer/Gemfile.lock
index a4210b3..3085696 100644
--- a/viewer/Gemfile.lock
+++ b/viewer/Gemfile.lock
@@ -80,7 +80,8 @@ GEM
     nokogiri (1.10.9)
       mini_portile2 (~> 2.4.0)
     pg (1.2.3)
-    puma (3.12.6)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -137,7 +138,7 @@ DEPENDENCIES
   byebug
   dotenv-rails
   pg (>= 0.18, < 2.0)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.4)
   tzinfo-data