diff --git a/ChangeLog b/ChangeLog
index 6f0c33da37..808bc7e1f4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jul 18 23:57:38 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* pack.c (pack_pack): round down too long uuencode width.  folding
+	  width in uuencode format cannot be longer than 63 bytes.
+
 Wed Jul 18 23:04:18 2012  NARUSE, Yui  <naruse@ruby-lang.org>
 
 	* ext/dbm/dbm.c (fdbm_empty_p): fix wrong condtion introduced in r36438.
diff --git a/pack.c b/pack.c
index 895d97c770..5b63c3f242 100644
--- a/pack.c
+++ b/pack.c
@@ -927,6 +927,8 @@ pack_pack(VALUE ary, VALUE fmt)
 	    }
 	    if (len <= 2)
 		len = 45;
+	    else if (len > 63 && type == 'u')
+		len = 63;
 	    else
 		len = len / 3 * 3;
 	    while (plen > 0) {
diff --git a/test/ruby/test_pack.rb b/test/ruby/test_pack.rb
index 5ea21d7827..c72035c2e7 100644
--- a/test/ruby/test_pack.rb
+++ b/test/ruby/test_pack.rb
@@ -496,6 +496,10 @@ class TestPack < Test::Unit::TestCase
     assert_equal("M86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A\n!80``\n", ["a"*46].pack("u0"))
     assert_equal("M86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A\n!80``\n", ["a"*46].pack("u1"))
     assert_equal("M86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A\n!80``\n", ["a"*46].pack("u2"))
+    assert_equal(<<EXPECTED, ["a"*80].pack("u68"))
+_86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A86%A
+186%A86%A86%A86%A86%A86$`
+EXPECTED
 
     assert_equal([""], "".unpack("u"))
     assert_equal(["a"], "!80``\n".unpack("u"))