diff --git a/Gemfile b/Gemfile
index 966fe6f6..2b3c6f46 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.3'
 # 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 e6b454e9..af4e3801 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -107,6 +107,7 @@ GEM
     faraday-rack (1.0.0)
     faraday_middleware (1.1.0)
       faraday (~> 1.0)
+    ffi (1.15.4)
     ffi (1.15.4-x64-mingw32)
     geom2d (0.3.1)
     globalid (0.5.2)
@@ -136,10 +137,13 @@ GEM
     nio4r (2.5.8)
     nokogiri (1.12.5-x64-mingw32)
       racc (~> 1.4)
+    nokogiri (1.12.5-x86_64-linux)
+      racc (~> 1.4)
     os (1.1.1)
     parslet (2.0.0)
     public_suffix (4.0.6)
-    puma (3.12.6)
+    puma (4.3.9)
+      nio4r (~> 2.0)
     racc (1.5.2)
     rack (2.2.3)
     rack-test (1.1.0)
@@ -228,6 +232,7 @@ GEM
 
 PLATFORMS
   x64-mingw32
+  x86_64-linux
 
 DEPENDENCIES
   actionview (>= 5.2.4.2)
@@ -248,7 +253,7 @@ DEPENDENCIES
   nokogiri (> 1.10.9)
   os (~> 1.1, >= 1.1.1)
   parslet
-  puma (~> 3.11)
+  puma (~> 4.3)
   rails (~> 5.2.3)
   ruby-rtf
   rubyzip (>= 1.3.0)