diff --git a/ChangeLog b/ChangeLog
index 18b6e0da4e..5edca53681 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Jan 12 16:09:02 2010  wanabe  <s.wanabe@gmail.com>
+
+	* test/ruby/test_process.rb (test_execopts_env): MANDATORY_ENVS might
+	  not be a part of ENV.  e.g. TMPDIR.
+
 Tue Jan 12 14:07:31 2010  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* lib/net/http.rb (Net::HTTP#start): add hash argument to
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index 949611ca1e..3a7eb5068f 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -238,7 +238,7 @@ class TestProcess < Test::Unit::TestCase
 
     h = {}
     cmd = [h, RUBY]
-    ENV.each do |k,v|
+    (ENV.keys + MANDATORY_ENVS).each do |k|
       case k
       when /\APATH\z/i
       when *MANDATORY_ENVS