diff --git a/ChangeLog b/ChangeLog
index 239dac9995..12031a53c0 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sat May  5 00:53:55 2012  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* io.c (parse_mode_enc): remove warnings 'Ignoring internal encoding'.
+	  [ruby-core:44455] [Bug #6324]
+
+	* io.c (io_encoding_set): ditto.
+
 Fri May  4 07:19:02 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* lib/rdoc/parser.rb (RDoc.binary?): fix wrong regexp.
diff --git a/io.c b/io.c
index 96087d6b0d..cacbe10247 100644
--- a/io.c
+++ b/io.c
@@ -4712,7 +4712,6 @@ parse_mode_enc(const char *estr, rb_encoding **enc_p, rb_encoding **enc2_p, int
 	    if (idx2 < 0)
 		unsupported_encoding(p);
 	    else if (idx2 == idx) {
-		rb_warn("Ignoring internal encoding %s: it is identical to external encoding %s", p, estr);
 		int_enc = (rb_encoding *)Qnil;
 	    }
 	    else
@@ -8788,8 +8787,6 @@ io_encoding_set(rb_io_t *fptr, VALUE v1, VALUE v2, VALUE opt)
 	    if (enc == enc2) {
 		/* Special case - "-" => no transcoding */
 		VALUE tmp1 = rb_check_string_type(v1);
-		rb_warn("Ignoring internal encoding %s: it is identical to external encoding %s",
-			StringValueCStr(tmp), NIL_P(tmp1) ? rb_enc_name(enc) : StringValueCStr(tmp1));
 		enc2 = NULL;
 	    }
 	}
@@ -8798,8 +8795,6 @@ io_encoding_set(rb_io_t *fptr, VALUE v1, VALUE v2, VALUE opt)
 	    if (enc == enc2) {
 		/* Special case - "-" => no transcoding */
 		VALUE tmp1 = rb_check_string_type(v1);
-		rb_warn("Ignoring internal encoding %s: it is identical to external encoding %s",
-			rb_enc_name(enc), NIL_P(tmp1) ? rb_enc_name(enc) : StringValueCStr(tmp1));
 		enc2 = NULL;
 	    }
 	}
diff --git a/test/ruby/test_io_m17n.rb b/test/ruby/test_io_m17n.rb
index be5bacf688..fcbe6e0519 100644
--- a/test/ruby/test_io_m17n.rb
+++ b/test/ruby/test_io_m17n.rb
@@ -985,26 +985,27 @@ EOT
   end
 
   def test_set_encoding_identical
-    bug5568 = '[ruby-core:40727]'
+    #bug5568 = '[ruby-core:40727]'
+    bug6324 = '[ruby-core:44455]'
     open(__FILE__, "r") do |f|
-      assert_warn(/Ignoring internal encoding euc-jp: it is identical to external encoding eucjp/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding("eucjp:euc-jp")
       }
-      assert_warn(/Ignoring internal encoding euc-jp: it is identical to external encoding eucjp/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding("eucjp", "euc-jp")
       }
-      assert_warn(/Ignoring internal encoding euc-jp: it is identical to external encoding EUC-JP/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding(Encoding::EUC_JP, "euc-jp")
       }
-      assert_warn(/Ignoring internal encoding EUC-JP: it is identical to external encoding eucjp/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding("eucjp", Encoding::EUC_JP)
       }
-      assert_warn(/Ignoring internal encoding EUC-JP: it is identical to external encoding EUC-JP/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding(Encoding::EUC_JP, Encoding::EUC_JP)
       }
       nonstr = Object.new
       def nonstr.to_str; "eucjp"; end
-      assert_warn(/Ignoring internal encoding eucjp: it is identical to external encoding eucjp/, bug5568) {
+      assert_warn('', bug6324) {
         f.set_encoding(nonstr, nonstr)
       }
     end