diff --git a/Gemfile b/Gemfile
index ae403fc..8187913 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,7 +14,7 @@ gem "foreman"
 gem "graphql"
 gem "jbuilder", "~> 2.5"
 gem "pg"
-gem "puma", "~> 3.11"
+gem "puma", "~> 4.3"
 gem "rails", "5.2.3"
 gem "sass-rails", "~> 5.0"
 gem "sprockets", "~> 3.7.2" # version 3.7.1 has a known vulnerability
diff --git a/Gemfile.lock b/Gemfile.lock
index 2724183..fb266ba 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -126,7 +126,9 @@ 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)
@@ -147,7 +149,8 @@ GEM
     pry-nav (0.3.0)
       pry (>= 0.9.10, < 0.13.0)
     public_suffix (3.1.1)
-    puma (3.12.1)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-proxy (0.6.5)
       rack
@@ -296,7 +299,7 @@ DEPENDENCIES
   pg
   pry
   pry-nav
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (= 5.2.3)
   rspec-rails
   sass-rails (~> 5.0)