diff --git a/ChangeLog b/ChangeLog
index 4788495c15..a74ca4c3b2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Jun 20 22:24:41 2013  Tanaka Akira  <akr@fsij.org>
+
+	* bignum.c (dump_bignum): Use SIZEOF_BDIGITS.
+
 Thu Jun 20 22:22:46 2013  Tanaka Akira  <akr@fsij.org>
 
 	* bignum.c (big2ulong): Change the return type to unsigned long.
diff --git a/bignum.c b/bignum.c
index 8de2e1a2c3..c39dcfda92 100644
--- a/bignum.c
+++ b/bignum.c
@@ -87,7 +87,7 @@ dump_bignum(VALUE x)
     long i;
     printf("%c0x0", RBIGNUM_SIGN(x) ? '+' : '-');
     for (i = RBIGNUM_LEN(x); i--; ) {
-	printf("_%08"PRIxBDIGIT, BDIGITS(x)[i]);
+        printf("_%0*"PRIxBDIGIT, SIZEOF_BDIGITS*2, BDIGITS(x)[i]);
     }
     printf(", len=%lu", RBIGNUM_LEN(x));
     puts("");