diff --git a/ChangeLog b/ChangeLog
index 290ea80f5f..4f10a73620 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sun Jul 11 11:07:42 2010  Yusuke Endoh  <mame@tsg.ne.jp>
+
+	* test/rdoc/test_rdoc_ri_driver.rb (test_formatter): add a test.  a
+	  patch from caleb clausen in [ruby-core:31182].
+
 Sat Jul 10 21:43:11 2010  Tanaka Akira  <akr@fsij.org>
 
 	* strftime.c (rb_strftime_with_timespec): fix precision handling for
diff --git a/test/rdoc/test_rdoc_ri_driver.rb b/test/rdoc/test_rdoc_ri_driver.rb
index 8d64916088..9ff89077b6 100644
--- a/test/rdoc/test_rdoc_ri_driver.rb
+++ b/test/rdoc/test_rdoc_ri_driver.rb
@@ -499,6 +499,10 @@ Foo::Bar#bother
     driver = RDoc::RI::Driver.new
 
     io = Object.new
+    def io.tty?; false; end
+
+    assert_instance_of @RM::ToBs, driver.formatter(io)
+
     def io.tty?; true; end
 
     assert_instance_of @RM::ToAnsi, driver.formatter(io)