diff --git a/Gemfile b/Gemfile
index 09ec410..66c0838 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,7 +7,7 @@ gem "rails", "~> 5.2"
 gem "sassc-rails", "~> 1.3"
 gem "uglifier", "~> 4.1"
 gem "sqlite3", "~> 1.3"
-gem "puma", "~> 3"
+gem "puma", "~> 4"
 gem "slim", "~> 3.0"
 gem "rbzip2", "~> 0.3"
 gem "dalli", "~> 2.7"
diff --git a/Gemfile.lock b/Gemfile.lock
index c8ab551..2073538 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -89,7 +89,9 @@ 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)
@@ -98,7 +100,8 @@ GEM
     nokogiri (1.10.4)
       mini_portile2 (~> 2.4.0)
     public_suffix (4.0.1)
-    puma (3.12.1)
+    puma (4.3.12)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -193,7 +196,7 @@ DEPENDENCIES
   chromedriver-helper
   dalli (~> 2.7)
   listen (>= 3.0.5, < 3.2)
-  puma (~> 3)
+  puma (~> 4)
   rails (~> 5.2)
   rbzip2 (~> 0.3)
   sassc-rails (~> 1.3)