diff --git a/ChangeLog b/ChangeLog
index 102eafb549..3207b2a717 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Fri May 23 15:16:16 2003  Nobuyoshi Nakada  <nobu.nokada@softhome.net>
+
+	* pack.c (pack_unpack): sign-extend if sizeof long is bigger than
+	  32.  (ruby-bugs-ja:PR#472)
+
 Thu May 22 18:07:46 2003  why the lucky stiff <ruby-cvs@whytheluckystiff.net>
 
 	* lib/token.c: single- and double-quoted root-level fix.
diff --git a/pack.c b/pack.c
index 58aa5d4105..b0b51c1b2a 100644
--- a/pack.c
+++ b/pack.c
@@ -351,6 +351,18 @@ num2u32(x)
 # endif
 #endif
 
+#if SIZEOF_LONG == SIZE32 || SIZEOF_INT == SIZE32
+# define EXTEND32(x) ((I32)(x))
+#else
+/* invariant in modulo 1<<31 */
+# define EXTEND32(x) (I32)(((1<<31)-1-(x))^~(~0<<31))
+#endif
+#if SIZEOF_SHORT == SIZE16
+# define EXTEND16(x) (short)(x)
+#else
+# define EXTEND16(x) (short)(((1<<15)-1-(x))^~(~0<<15))
+#endif
+
 #ifdef HAVE_LONG_LONG
 # define QUAD_SIZE sizeof(LONG_LONG)
 #else
@@ -1317,6 +1329,9 @@ pack_unpack(str, fmt)
 	    while (len-- > 0) {
 		short tmp = 0;
 		memcpy(OFF16(&tmp), s, NATINT_LEN(short,2));
+#if SIZEOF_SHORT != SIZE16
+		if (!natint) tmp = EXTEND16(tmp);
+#endif
 		s += NATINT_LEN(short,2);
 		rb_ary_push(ary, INT2FIX(tmp));
 	    }
@@ -1361,6 +1376,9 @@ pack_unpack(str, fmt)
 	    while (len-- > 0) {
 		long tmp = 0;
 		memcpy(OFF32(&tmp), s, NATINT_LEN(long,4));
+#if SIZEOF_LONG != SIZE32
+		if (!natint) tmp = EXTEND32(tmp);
+#endif
 		s += NATINT_LEN(long,4);
 		rb_ary_push(ary, LONG2NUM(tmp));
 	    }