diff --git a/Gemfile b/Gemfile
index 0a85044..7e2e10e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -11,7 +11,7 @@ end
 gem 'rails', '~> 5.2.3'
 
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 
 # Use SCSS for stylesheets
 gem 'sassc-rails'
diff --git a/Gemfile.lock b/Gemfile.lock
index 549f47d..1b5be74 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -169,7 +169,9 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mimemagic (0.3.3)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.2)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
@@ -211,7 +213,8 @@ GEM
     pg (0.21.0)
     popper_js (1.14.5)
     public_suffix (3.1.1)
-    puma (3.12.4)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -377,7 +380,7 @@ DEPENDENCIES
   omniauth-twitter
   pagy
   pg (~> 0.18)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   rails-controller-testing
   random_password