diff --git a/Gemfile b/Gemfile
index 2cffd22..71e2e83 100644
--- a/Gemfile
+++ b/Gemfile
@@ -27,7 +27,7 @@ gem 'json', '~> 2.3'
 # gem "sinatra", require: "sinatra/base"
 # gem "sinatra-contrib", require: ["sinatra/namespace", "sinatra/reloader"]
 # gem "sinatra-router"
-gem 'puma', '~> 3.9'
+gem 'puma', '~> 4.3'
 
 ## Time & Space
 gem 'ice_cube', '~> 0.16.0' # Date/Time helper
diff --git a/Gemfile.lock b/Gemfile.lock
index 2bb2193..6343b7b 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -179,6 +179,7 @@ GEM
     multi_xml (0.6.0)
     multipart-post (2.1.1)
     nenv (0.3.0)
+    nio4r (2.5.8)
     notiffany (0.1.3)
       nenv (~> 0.1)
       shellany (~> 0.0)
@@ -216,7 +217,8 @@ GEM
       pry (~> 0.10)
     pry-nav (0.2.4)
       pry (>= 0.9.10, < 0.11.0)
-    puma (3.12.6)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     raabro (1.4.0)
     rack (1.6.13)
     rack-accept (0.4.5)
@@ -348,7 +350,7 @@ DEPENDENCIES
   pry
   pry-byebug (~> 3.4)
   pry-nav (~> 0.2.4)
-  puma (~> 3.9)
+  puma (~> 4.3)
   rack-test (~> 0.6.3)
   rack-timeout (~> 0.4)
   rake (~> 10.5)