diff --git a/Gemfile b/Gemfile
index b8b2e54..422c442 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,7 +16,7 @@ gem 'rails', '~> 5.2.2'
 # 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'
 # 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 3c7926d..7aa8fda 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -124,7 +124,9 @@ 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 (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
@@ -139,7 +141,8 @@ GEM
     orm_adapter (0.5.0)
     popper_js (1.14.5)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.6)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -253,7 +256,7 @@ DEPENDENCIES
   letter_opener
   listen (>= 3.0.5, < 3.2)
   octokit (~> 4.0)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.2)
   rails-i18n (~> 5.1.0)
   sass-rails (~> 5.0)