diff --git a/ChangeLog b/ChangeLog
index 4d227955db..6c937543db 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,4 @@
-Fri Jul  5 16:01:21 2013  Akinori MUSHA  <knu@iDaemons.org>
+Fri Jul  5 16:21:56 2013  Akinori MUSHA  <knu@iDaemons.org>
 
 	* test/ruby/test_regexp.rb
 	  (TestRegexp#test_options_in_look_behind)
@@ -8,6 +8,11 @@ Fri Jul  5 16:01:21 2013  Akinori MUSHA  <knu@iDaemons.org>
 	  interpolate a regexp into another in the middle of a look-behind
 	  pattern.  cf. https://github.com/k-takata/Onigmo/pull/17
 
+	* test/ruby/test_regexp.rb
+	  (TestRegexp#test_options_in_look_behind)
+	  (TestRegexp#assert_match_at): Parse regexps in run time rather
+	  than in compile time.
+
 Fri Jul  5 12:14:40 2013  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* test/ruby/test_rubyoptions.rb (TestRubyOptions#test_notfound): after
diff --git a/test/ruby/test_regexp.rb b/test/ruby/test_regexp.rb
index 2bfbd9dff9..11e86ec09d 100644
--- a/test/ruby/test_regexp.rb
+++ b/test/ruby/test_regexp.rb
@@ -946,19 +946,22 @@ class TestRegexp < Test::Unit::TestCase
 
   def test_options_in_look_behind
     assert_nothing_raised {
-      assert_match_at(/(?<=(?i)ab)cd/, "ABcd", [[2,4]])
-      assert_match_at(/(?<=(?i:ab))cd/, "ABcd", [[2,4]])
-      assert_match_at(/(?<!(?i)ab)cd/, "aacd", [[2,4]])
-      assert_match_at(/(?<!(?i:ab))cd/, "aacd", [[2,4]])
+      assert_match_at("(?<=(?i)ab)cd", "ABcd", [[2,4]])
+      assert_match_at("(?<=(?i:ab))cd", "ABcd", [[2,4]])
+      assert_match_at("(?<!(?i)ab)cd", "aacd", [[2,4]])
+      assert_match_at("(?<!(?i:ab))cd", "aacd", [[2,4]])
 
-      assert_not_match(/(?<=(?i)ab)cd/, "ABCD")
-      assert_not_match(/(?<=(?i:ab))cd/, "ABCD")
-      assert_not_match(/(?<!(?i)ab)cd/, "ABcd")
-      assert_not_match(/(?<!(?i:ab))cd/, "ABcd")
+      assert_not_match("(?<=(?i)ab)cd", "ABCD")
+      assert_not_match("(?<=(?i:ab))cd", "ABCD")
+      assert_not_match("(?<!(?i)ab)cd", "ABcd")
+      assert_not_match("(?<!(?i:ab))cd", "ABcd")
     }
   end
 
+  # This assertion is for porting x2() tests in testpy.py of Onigmo.
   def assert_match_at(re, str, positions, msg = nil)
+    re = Regexp.new(re) unless re.is_a?(Regexp)
+
     match = re.match(str)
 
     assert_not_nil match, message(msg) {