diff --git a/tool/test_for_warn_bundled_gems/test_warn_bundled_gems.rb b/tool/test_for_warn_bundled_gems/test_warn_bundled_gems.rb
index bd0e184f7f..a8f065a6b0 100644
--- a/tool/test_for_warn_bundled_gems/test_warn_bundled_gems.rb
+++ b/tool/test_for_warn_bundled_gems/test_warn_bundled_gems.rb
@@ -7,5 +7,7 @@ gemfile do
   source "https://rubygems.org"
 end
 
+Object.send(:remove_const, :Bundler)
+
 require "mutex_m"
 require "rss"