diff --git a/Gemfile b/Gemfile
index 97a3ae2..2600e34 100644
--- a/Gemfile
+++ b/Gemfile
@@ -3,7 +3,7 @@ source "https://rubygems.org"
 gem "rails", "~> 5.1.2"
 gem "pg"
 # Use Puma as the app server
-gem "puma", "~> 3.7"
+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 e0a1ef3..5495997 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -128,7 +128,9 @@ GEM
     mime-types (3.1)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
-    mimemagic (0.3.2)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_portile2 (2.2.0)
     minitest (5.10.3)
     mize (0.3.2)
@@ -174,7 +176,8 @@ GEM
       byebug (~> 9.0)
       pry (~> 0.10)
     public_suffix (2.0.5)
-    puma (3.9.1)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.3)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -320,7 +323,7 @@ DEPENDENCIES
   pg
   pry
   pry-byebug
-  puma (~> 3.7)
+  puma (~> 4.3)
   rails (~> 5.1.2)
   rspec-rails (~> 3.6)
   rspec-retry