diff --git a/.rubocop.yml b/.rubocop.yml
index 8fd406e..df528bf 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -1,6 +1,6 @@
 ---
 require:
-  - chefstyle
+  - cookstyle
 
 AllCops:
   TargetRubyVersion: 3.1
diff --git a/Gemfile b/Gemfile
index c29f133..c441101 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,6 +16,6 @@ group :debug do
   gem "pry"
 end
 
-group :chefstyle do
-  gem "chefstyle", "2.2.3"
+group :cookstyle do
+  gem "cookstyle"
 end
diff --git a/Rakefile b/Rakefile
index 982e39d..d75e210 100644
--- a/Rakefile
+++ b/Rakefile
@@ -15,13 +15,13 @@ task :stats do
 end
 
 begin
-  require "chefstyle"
+  require "cookstyle"
   require "rubocop/rake_task"
   RuboCop::RakeTask.new(:style) do |task|
-    task.options += ["--display-cop-names", "--no-color"]
+    task.options += ["--chefstyle", "--display-cop-names", "--no-color"]
   end
 rescue LoadError
-  puts "chefstyle is not available.  gem install chefstyle to do style checking."
+  puts "cookstyle is not available.  gem install cookstyle to do style checking."
 end
 
 desc "Run all quality tasks"
diff --git a/lib/kitchen/driver/openstack.rb b/lib/kitchen/driver/openstack.rb
index 1365b46..ac53857 100755
--- a/lib/kitchen/driver/openstack.rb
+++ b/lib/kitchen/driver/openstack.rb
@@ -178,12 +178,12 @@ def create_server
         raise(ActionFailed, "Cannot specify both network_ref and network_id") if config[:network_id] && config[:network_ref]
 
         if config[:network_id]
-          networks = [].concat([config[:network_id]])
+          networks = [].push(config[:network_id])
           server_def[:nics] = networks.flatten.map do |net_id|
             { "net_id" => net_id }
           end
         elsif config[:network_ref]
-          networks = [].concat([config[:network_ref]])
+          networks = [].push(config[:network_ref])
           server_def[:nics] = networks.flatten.map do |net|
             { "net_id" => find_network(net).id }
           end