diff --git a/Gemfile b/Gemfile
index 5266623..30358a4 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,7 +5,7 @@ ruby '2.6.2'
 
 # Web API
 gem 'json'
-gem 'puma', '~>3.11'
+gem 'puma', '~>4.3'
 gem 'rack', '>= 2.0.6'
 gem 'roda', '~>3.6'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 8073964..5e473d5 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -36,6 +36,7 @@ GEM
     minitest (5.11.3)
     minitest-rg (5.2.0)
       minitest (~> 5.0)
+    nio4r (2.5.7)
     parallel (1.17.0)
     parser (2.6.2.1)
       ast (~> 2.4.0)
@@ -45,7 +46,8 @@ GEM
       method_source (~> 0.9.0)
     psych (3.1.0)
     public_suffix (3.0.3)
-    puma (3.12.1)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -105,7 +107,7 @@ DEPENDENCIES
   minitest-rg
   pg
   pry
-  puma (~> 3.11)
+  puma (~> 4.3)
   rack (>= 2.0.6)
   rack-test
   rake