diff --git a/lib/bundled_gems.rb b/lib/bundled_gems.rb
index 2a00e83a46..96489257d7 100644
--- a/lib/bundled_gems.rb
+++ b/lib/bundled_gems.rb
@@ -53,7 +53,7 @@ module Gem::BUNDLED_GEMS
   WARNED = {}                   # unfrozen
 
   conf = ::RbConfig::CONFIG
-  if ENV["TEST_BUNDLED_GEMS"]
+  if ENV["TEST_BUNDLED_GEMS_FAKE_RBCONFIG"]
     LIBDIR = (File.expand_path(File.join(__dir__, "..", "lib")) + "/").freeze
     rubyarchdir = $LOAD_PATH.find{|path| path.include?(".ext/common") }
     ARCHDIR = (File.expand_path(rubyarchdir) + "/").freeze
diff --git a/spec/bundled_gems_spec.rb b/spec/bundled_gems_spec.rb
index 90c447ace5..7da8380cf0 100644
--- a/spec/bundled_gems_spec.rb
+++ b/spec/bundled_gems_spec.rb
@@ -20,7 +20,7 @@ RSpec.configure do |config|
 
   config.before(:suite) do
     Gem.ruby = ENV["RUBY"] if ENV["RUBY"]
-    ENV["TEST_BUNDLED_GEMS"] = "true"
+    ENV["TEST_BUNDLED_GEMS_FAKE_RBCONFIG"] = "true"
 
     require_relative "bundler/support/rubygems_ext"
     Spec::Rubygems.test_setup