diff --git a/ChangeLog b/ChangeLog
index e97b238d0a..e10aead0e9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -18,6 +18,11 @@ Wed Oct 29 20:45:08 2008  Yusuke Endoh  <mame@tsg.ne.jp>
 	  test/webrick/test_server.rb, test/webrick/test_filehandler.rb: use
 	  webrick log as an assertion message.
 
+Wed Oct 29 16:41:17 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* pack.c (pack_pack): set encoding from packing string and UTF-8 for
+	  "U".  [ruby-core:19590]
+
 Wed Oct  29 15:50:00 2008  TAKANO Mitsuhiro (takano32)  <tak@no32.tk>
 
 	* complex.c (imp1, imp2): should declare type.
diff --git a/pack.c b/pack.c
index 9641f6e407..df25231610 100644
--- a/pack.c
+++ b/pack.c
@@ -10,6 +10,7 @@
 **********************************************************************/
 
 #include "ruby/ruby.h"
+#include "ruby/encoding.h"
 #include <sys/types.h>
 #include <ctype.h>
 #include <errno.h>
@@ -443,6 +444,7 @@ pack_pack(VALUE ary, VALUE fmt)
     char type;
     long items, len, idx, plen;
     const char *ptr;
+    rb_encoding *enc;
 #ifdef NATINT_PACK
     int natint;		/* native integer */
 #endif
@@ -517,6 +519,8 @@ pack_pack(VALUE ary, VALUE fmt)
 		ptr = RSTRING_PTR(from);
 		plen = RSTRING_LEN(from);
 		OBJ_INFECT(res, from);
+		enc = rb_enc_compatible(res, from);
+		rb_enc_associate(res, enc);
 	    }
 
 	    if (p[-1] == '*')
@@ -865,6 +869,8 @@ pack_pack(VALUE ary, VALUE fmt)
 	    break;
 
 	  case 'U':		/* Unicode character */
+	    enc = rb_enc_compatible(res, rb_enc_from_encoding(rb_utf8_encoding()));
+	    rb_enc_associate(res, enc);
 	    while (len-- > 0) {
 		SIGNED_VALUE l;
 		char buf[8];
diff --git a/test/ruby/test_array.rb b/test/ruby/test_array.rb
index f3ee624bf0..fcc493951f 100644
--- a/test/ruby/test_array.rb
+++ b/test/ruby/test_array.rb
@@ -888,7 +888,7 @@ class TestArray < Test::Unit::TestCase
     assert_equal("aGVsbG8K\n",  @cls["hello\n"].pack("m"))
     assert_equal(",:&5L;&\\*:&5L;&\\*\n",  @cls["hello\nhello\n"].pack("u"))
 
-    assert_equal("\xc2\xa9B\xe2\x89\xa0", @cls[0xa9, 0x42, 0x2260].pack("U*"))
+    assert_equal("\u{a9 42 2260}", @cls[0xa9, 0x42, 0x2260].pack("U*"))
 
 
     format = "c2x5CCxsdils_l_a6";
diff --git a/test/ruby/test_pack.rb b/test/ruby/test_pack.rb
index 22b7b87580..2666bb0e90 100644
--- a/test/ruby/test_pack.rb
+++ b/test/ruby/test_pack.rb
@@ -51,9 +51,9 @@ class TestPack < Test::Unit::TestCase
     assert_raise(RangeError) { [-0x40000000].pack("U") }
     assert_raise(RangeError) { [-1].pack("U") }
     assert_equal "\000", [0].pack("U")
-    assert_equal "\374\277\277\277\277\277", [0x3fffffff].pack("U")
-    assert_equal "\375\200\200\200\200\200", [0x40000000].pack("U")
-    assert_equal "\375\277\277\277\277\277", [0x7fffffff].pack("U")
+    assert_equal "\374\277\277\277\277\277".force_encoding(Encoding::UTF_8), [0x3fffffff].pack("U")
+    assert_equal "\375\200\200\200\200\200".force_encoding(Encoding::UTF_8), [0x40000000].pack("U")
+    assert_equal "\375\277\277\277\277\277".force_encoding(Encoding::UTF_8), [0x7fffffff].pack("U")
     assert_raise(RangeError) { [0x80000000].pack("U") }
     assert_raise(RangeError) { [0x100000000].pack("U") }
   end