diff --git a/ChangeLog b/ChangeLog
index e09b1d572f..4109dc2fcf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed May 12 09:21:05 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* re.c (rb_reg_initialize_m): fix wrong index for the lang
+	  option's value 'N'. reported by Masaya TARUI via IRC.
+
 Tue May 11 23:07:22 2010  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/extconf.rb: test IPPROTO_IP and IPPROTO_IPV6 constants.
diff --git a/re.c b/re.c
index b1e5c1d34d..e4f1968733 100644
--- a/re.c
+++ b/re.c
@@ -2894,7 +2894,7 @@ rb_reg_initialize_m(int argc, VALUE *argv, VALUE self)
 	enc = 0;
 	if (argc == 3 && !NIL_P(argv[2])) {
 	    char *kcode = StringValuePtr(argv[2]);
-	    if (kcode[0] == 'n' || kcode[1] == 'N') {
+	    if (kcode[0] == 'n' || kcode[0] == 'N') {
 		enc = rb_ascii8bit_encoding();
 		flags |= ARG_ENCODING_NONE;
 	    }
diff --git a/test/ruby/test_regexp.rb b/test/ruby/test_regexp.rb
index 00c2ddb5e9..888a0cb9e5 100644
--- a/test/ruby/test_regexp.rb
+++ b/test/ruby/test_regexp.rb
@@ -286,6 +286,10 @@ class TestRegexp < Test::Unit::TestCase
     assert_equal("bar", "foobarbaz"[Regexp.new("b..", nil, "n")])
     assert_equal(//n, Regexp.new("", nil, "n"))
 
+    arg_encoding_none = 32 # ARG_ENCODING_NONE is implementation defined value
+    assert_equal(arg_encoding_none, Regexp.new("", nil, "n").options)
+    assert_equal(arg_encoding_none, Regexp.new("", nil, "N").options)
+
     assert_raise(RegexpError) { Regexp.new(")(") }
   end