diff --git a/spec/bundler/support/rubygems_ext.rb b/spec/bundler/support/rubygems_ext.rb
index 0d1ad2d528..889ebc90c3 100644
--- a/spec/bundler/support/rubygems_ext.rb
+++ b/spec/bundler/support/rubygems_ext.rb
@@ -38,6 +38,10 @@ module Spec
       FileUtils.mkdir_p(Path.tmpdir)
 
       ENV["HOME"] = Path.home.to_s
+      # Remove "RUBY_CODESIGN", which is used by mkmf-generated Makefile to
+      # sign extension bundles on macOS, to avoid trying to find the specified key
+      # from the fake $HOME/Library/Keychains directory.
+      ENV.delete "RUBY_CODESIGN"
       ENV["TMPDIR"] = Path.tmpdir.to_s
 
       require "rubygems/user_interaction"
diff --git a/test/rubygems/helper.rb b/test/rubygems/helper.rb
index 9ca2e269e3..ed9e34a906 100644
--- a/test/rubygems/helper.rb
+++ b/test/rubygems/helper.rb
@@ -351,6 +351,10 @@ class Gem::TestCase < Test::Unit::TestCase
     Dir.chdir @tempdir
 
     ENV["HOME"] = @userhome
+    # Remove "RUBY_CODESIGN", which is used by mkmf-generated Makefile to
+    # sign extension bundles on macOS, to avoid trying to find the specified key
+    # from the fake $HOME/Library/Keychains directory.
+    ENV.delete "RUBY_CODESIGN"
     Gem.instance_variable_set :@config_file, nil
     Gem.instance_variable_set :@user_home, nil
     Gem.instance_variable_set :@config_home, nil