diff --git a/Gemfile b/Gemfile
index 0f7362e..50f12b9 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'
 # 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 dc0fa4c..a62dead 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -86,7 +86,7 @@ GEM
     jbuilder (2.8.0)
       activesupport (>= 4.2.0)
       multi_json (>= 1.2)
-    libv8 (6.7.288.46.1-x86_64-linux)
+    libv8 (6.7.288.46.1)
     listen (3.1.5)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -99,7 +99,9 @@ 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)
     mini_racer (0.2.4)
@@ -113,7 +115,8 @@ GEM
     orm_adapter (0.5.0)
     pg (1.1.4)
     public_suffix (3.0.3)
-    puma (3.12.1)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.0.6)
     rack-proxy (0.6.5)
       rack
@@ -223,7 +226,7 @@ DEPENDENCIES
   listen (>= 3.0.5, < 3.2)
   mini_racer
   pg
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.2, >= 5.2.2.1)
   react_on_rails (= 11.2.1)
   sass-rails (~> 5.0)