diff --git a/.github/workflows/mri.yml b/.github/workflows/mri.yml
index b81828f3..2f28ae5f 100644
--- a/.github/workflows/mri.yml
+++ b/.github/workflows/mri.yml
@@ -59,6 +59,13 @@ jobs:
         continue-on-error: true
         timeout-minutes: 5
 
+      # Fix RubyGems warnings about required_ruby_version bug with Bundler
+      - name: update rubygems for Ruby 2.3 - 2.5
+        if: matrix.ruby >= '2.3' && matrix.ruby < '2.6'
+        run: gem update --system 3.2.3 --no-document
+        continue-on-error: true
+        timeout-minutes: 5
+
       - name: Compile Puma without SSL support
         if: matrix.no-ssl == ' no SSL'
         shell: bash
@@ -72,8 +79,6 @@ jobs:
         run:  bundle exec rake compile
 
       - name: rubocop
-        # 2021-05-20 - RuboCop won't run with Psych 4.0 - remove when fixed
-        if: (endsWith(matrix.ruby, 'head') == false) && (endsWith(matrix.ruby, 'ucrt') == false)
         run: bundle exec rake rubocop
 
       - name: Use yjit
diff --git a/Gemfile b/Gemfile
index 727ee281..f40b2674 100644
--- a/Gemfile
+++ b/Gemfile
@@ -16,7 +16,7 @@ gem "sd_notify"
 
 gem "jruby-openssl", :platform => "jruby"
 
-gem "rubocop", "~> 0.58.0"
+gem "rubocop", "~> 0.64.0"
 
 if %w(2.2.7 2.2.8 2.2.9 2.2.10 2.3.4 2.4.1).include? RUBY_VERSION
   gem "stopgap_13632", "~> 1.0", :platforms => ["mri", "mingw", "x64_mingw"]
diff --git a/lib/puma/thread_pool.rb b/lib/puma/thread_pool.rb
index 9454564f..e3e1915a 100644
--- a/lib/puma/thread_pool.rb
+++ b/lib/puma/thread_pool.rb
@@ -72,7 +72,7 @@ module Puma
     attr_accessor :out_of_band_hook # @version 5.0.0
 
     def self.clean_thread_locals
-      Thread.current.keys.each do |key| # rubocop: disable Performance/HashEachMethods
+      Thread.current.keys.each do |key| # rubocop: disable Style/HashEachMethods
         Thread.current[key] = nil unless key == :__recursive_key__
       end
     end