diff --git a/ChangeLog b/ChangeLog
index f80544c28e..ab2f0997d1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Thu Nov 22 12:52:19 2012  Akinori MUSHA  <knu@iDaemons.org>
+
+	* test/ruby/test_string.rb (TestString#test_index): Add some
+	  corner cases to tests for String#index, which might fail if ruby
+	  directly used a buggy memmem(3) implementation.
+
 Thu Nov 22 08:06:42 2012  Narihiro Nakamura  <authornari@gmail.com>
 
 	* test/ruby/test_gc.rb (test_profiler_clear): fix wrong method
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 2beaef3504..2e63eff5a7 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -830,6 +830,13 @@ class TestString < Test::Unit::TestCase
     assert_nil(S("hello").index(S("z")))
     assert_nil(S("hello").index(/z./))
 
+    assert_equal(0, S("").index(S("")))
+    assert_equal(0, S("").index(//))
+    assert_nil(S("").index(S("hello")))
+    assert_nil(S("").index(/hello/))
+    assert_equal(0, S("hello").index(S("")))
+    assert_equal(0, S("hello").index(//))
+
     o = Object.new
     def o.to_str; "bar"; end
     assert_equal(3, "foobarbarbaz".index(o))