diff --git a/ChangeLog b/ChangeLog
index 709f75264e..3a7f8df0b9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jul 31 12:23:53 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* pack.c (pack_unpack): upper half of hexdigits has never been used.
+
 Thu Jul 31 11:31:29 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/syck/syck.h (ASSERT): fix typo at r18176.
diff --git a/pack.c b/pack.c
index b22a8348b2..610cb30a0f 100644
--- a/pack.c
+++ b/pack.c
@@ -1304,7 +1304,7 @@ static VALUE
 pack_unpack(str, fmt)
     VALUE str, fmt;
 {
-    static const char hexdigits[] = "0123456789abcdef0123456789ABCDEFx";
+    static const char hexdigits[] = "0123456789abcdef";
     char *s, *send;
     char *p, *pend;
     VALUE ary;