diff --git a/ChangeLog b/ChangeLog
index ce3cbdf7f3..5fa7e5f23f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue May 31 12:40:49 2011  NAKAMURA Usaku  <usa@ruby-lang.org>
+
+	* test/ruby/test_io.rb (TestIO#test_open_mode): MUST release resources
+	  explicitly. fix problem of r31671
+
 Tue May 31 10:49:55 2011  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* vm_exec.c: remove conditions for clang
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index f91922796d..73cef715e6 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -1854,10 +1854,14 @@ End
     feature4742 = "[ruby-core:36338]"
 
     mkcdtmpdir do
-      refute_nil(File.open('symbolic', 'w'))
-      refute_nil(File.open('numeric',  File::WRONLY|File::TRUNC|File::CREAT))
-      refute_nil(File.open('hash-symbolic', :mode => 'w'))
-      refute_nil(File.open('hash-numeric', :mode => File::WRONLY|File::TRUNC|File::CREAT), feature4742)
+      refute_nil(f = File.open('symbolic', 'w'))
+      f.close
+      refute_nil(f = File.open('numeric',  File::WRONLY|File::TRUNC|File::CREAT))
+      f.close
+      refute_nil(f = File.open('hash-symbolic', :mode => 'w'))
+      f.close
+      refute_nil(f = File.open('hash-numeric', :mode => File::WRONLY|File::TRUNC|File::CREAT), feature4742)
+      f.close
     end
   end