diff --git a/ChangeLog b/ChangeLog
index f808ca0b80..784f8afc4f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat Aug  8 11:42:44 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* bignum.c (bigzero_p): removing BDIGITS() inside of the
+	  loop. inspired by Hitohiro Kanai's blog entry
+	  <http://d.hatena.ne.jp/CanI/20090807/1249657492>.
+
 Sat Aug  8 06:18:29 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* marshal.c (w_symbol r_symlink, r_symbol, r_object0): fix for
diff --git a/bignum.c b/bignum.c
index bd9e0c8cae..9fa1f2aab3 100644
--- a/bignum.c
+++ b/bignum.c
@@ -46,8 +46,10 @@ static int
 bigzero_p(VALUE x)
 {
     long i;
+    BDIGIT *ds = BDIGITS(x);
+
     for (i = RBIGNUM_LEN(x) - 1; 0 <= i; i--) {
-	if (BDIGITS(x)[i]) return 0;
+	if (ds[i]) return 0;
     }
     return 1;
 }