diff --git a/Gemfile b/Gemfile
index c00190d..59063ce 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,3 +13,4 @@ gem 'rack-proxy'
 gem 'websocket-driver'
 gem 'eventmachine'
 gem 'puma'
+gem 'rackup'
diff --git a/Gemfile.lock b/Gemfile.lock
index e438c0b..a6ed55c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -4,7 +4,6 @@ PATH
     diver_down (0.1.0)
       activesupport (>= 7.0.0)
       msgpack (>= 1.7.0)
-      rackup
 
 GEM
   remote: https://rubygems.org/
@@ -99,6 +98,7 @@ DEPENDENCIES
   puma
   rack-proxy
   rack-test
+  rackup
   rake (~> 13.0)
   rspec (~> 3.0)
   rubocop (~> 1.21)
diff --git a/diver_down.gemspec b/diver_down.gemspec
index 7e4e5b3..57559d6 100644
--- a/diver_down.gemspec
+++ b/diver_down.gemspec
@@ -27,5 +27,4 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'activesupport', '>= 7.0.0'
   spec.add_dependency 'msgpack', '>= 1.7.0'
-  spec.add_dependency 'rackup'
 end
diff --git a/exe/diver_down_web b/exe/diver_down_web
index 1c606c0..47186b5 100755
--- a/exe/diver_down_web
+++ b/exe/diver_down_web
@@ -2,8 +2,8 @@
 # frozen_string_literal: true
 
 require 'bundler/setup'
-require 'rackup'
 require 'webrick'
+require 'rackup'
 require 'diver_down'
 require 'diver_down-web'