diff --git "a/3\347\253\240/Gemfile" "b/3\347\253\240/Gemfile"
index fa4871d..a38d9c9 100644
--- "a/3\347\253\240/Gemfile"
+++ "b/3\347\253\240/Gemfile"
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.3'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.4.1' # Rails 5.2.3より前のバージョンに配慮してバージョンを指定する。
 # 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/3\347\253\240/Gemfile.lock" "b/3\347\253\240/Gemfile.lock"
index 6b0b433..c4c8ae7 100644
--- "a/3\347\253\240/Gemfile.lock"
+++ "b/3\347\253\240/Gemfile.lock"
@@ -75,7 +75,9 @@ 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)
@@ -83,7 +85,8 @@ GEM
     nio4r (2.4.0)
     nokogiri (1.10.3)
       mini_portile2 (~> 2.4.0)
-    puma (3.12.1)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -183,7 +186,7 @@ DEPENDENCIES
   byebug
   factory_bot_rails (~> 5.0)
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   rspec-rails (~> 3.8)
   sass-rails (~> 5.0)