diff --git a/ChangeLog b/ChangeLog
index 17dfe5b6d8..d218a64d6d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jun  8 22:18:57 2013  Tanaka Akira  <akr@fsij.org>
+
+	* time.c (v2w): Use rb_absint_size instead of RBIGNUM_LEN.
+
 Sat Jun  8 21:47:33 2013  Tanaka Akira  <akr@fsij.org>
 
 	* time.c (v2w_bignum): Simplified using rb_integer_pack.
diff --git a/time.c b/time.c
index 81306bfe7a..61b9d3e1a8 100644
--- a/time.c
+++ b/time.c
@@ -326,7 +326,7 @@ v2w(VALUE v)
         return WIDEVAL_WRAP((WIDEVALUE)(SIGNED_WIDEVALUE)(long)v);
     }
     else if (RB_TYPE_P(v, T_BIGNUM) &&
-        RBIGNUM_LEN(v) * sizeof(BDIGIT) <= sizeof(WIDEVALUE)) {
+        rb_absint_size(v, NULL) <= sizeof(WIDEVALUE)) {
         return v2w_bignum(v);
     }
 #endif