diff --git a/lib/bundler/rubygems_integration.rb b/lib/bundler/rubygems_integration.rb
index d70d606f57f0f4..da555681f98aba 100644
--- a/lib/bundler/rubygems_integration.rb
+++ b/lib/bundler/rubygems_integration.rb
@@ -4,17 +4,12 @@
 
 module Bundler
   class RubygemsIntegration
-    if defined?(Gem::Ext::Builder::CHDIR_MONITOR)
-      EXT_LOCK = Gem::Ext::Builder::CHDIR_MONITOR
-    else
-      require "monitor"
+    require "monitor"
 
-      EXT_LOCK = Monitor.new
-    end
+    EXT_LOCK = Monitor.new
 
     def initialize
       @replaced_methods = {}
-      backport_ext_builder_monitor
     end
 
     def version
@@ -479,25 +474,6 @@ def all_specs
       end
     end
 
-    def backport_ext_builder_monitor
-      # So we can avoid requiring "rubygems/ext" in its entirety
-      Gem.module_eval <<-RUBY, __FILE__, __LINE__ + 1
-        module Ext
-        end
-      RUBY
-
-      require "rubygems/ext/builder"
-
-      Gem::Ext::Builder.class_eval do
-        unless const_defined?(:CHDIR_MONITOR)
-          const_set(:CHDIR_MONITOR, EXT_LOCK)
-        end
-
-        remove_const(:CHDIR_MUTEX) if const_defined?(:CHDIR_MUTEX)
-        const_set(:CHDIR_MUTEX, const_get(:CHDIR_MONITOR))
-      end
-    end
-
     def find_bundler(version)
       find_name("bundler").find {|s| s.version.to_s == version }
     end
diff --git a/spec/bundler/bundler/plugin/installer_spec.rb b/spec/bundler/bundler/plugin/installer_spec.rb
index bbca97e9470673..2cf69649db00b9 100644
--- a/spec/bundler/bundler/plugin/installer_spec.rb
+++ b/spec/bundler/bundler/plugin/installer_spec.rb
@@ -6,7 +6,6 @@
   describe "cli install" do
     it "uses Gem.sources when non of the source is provided" do
       sources = double(:sources)
-      Bundler.settings # initialize it before we have to touch rubygems.ext_lock
       allow(Gem).to receive(:sources) { sources }
 
       allow(installer).to receive(:install_rubygems).
diff --git a/spec/bundler/bundler/rubygems_integration_spec.rb b/spec/bundler/bundler/rubygems_integration_spec.rb
index d4e6957a018f44..431f1256e3261b 100644
--- a/spec/bundler/bundler/rubygems_integration_spec.rb
+++ b/spec/bundler/bundler/rubygems_integration_spec.rb
@@ -1,10 +1,6 @@
 # frozen_string_literal: true
 
 RSpec.describe Bundler::RubygemsIntegration do
-  it "uses the same chdir lock as rubygems" do
-    expect(Bundler.rubygems.ext_lock).to eq(Gem::Ext::Builder::CHDIR_MONITOR)
-  end
-
   context "#validate" do
     let(:spec) do
       Gem::Specification.new do |s|
diff --git a/spec/bundler/bundler/shared_helpers_spec.rb b/spec/bundler/bundler/shared_helpers_spec.rb
index d40a1afde3da7b..918f73b3379b3e 100644
--- a/spec/bundler/bundler/shared_helpers_spec.rb
+++ b/spec/bundler/bundler/shared_helpers_spec.rb
@@ -1,12 +1,8 @@
 # frozen_string_literal: true
 
 RSpec.describe Bundler::SharedHelpers do
-  let(:ext_lock_double) { double(:ext_lock) }
-
   before do
     pwd_stub
-    allow(Bundler.rubygems).to receive(:ext_lock).and_return(ext_lock_double)
-    allow(ext_lock_double).to receive(:synchronize) {|&block| block.call }
   end
 
   let(:pwd_stub) { allow(subject).to receive(:pwd).and_return(bundled_app) }