diff --git a/ChangeLog b/ChangeLog
index 097b928e34..ef628f4f21 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jun 15 22:35:31 2009  Tadayoshi Funaba  <tadf@dotrb.org>
+
+	* bignum.c (rb_big2db): (-Float::MAX.to_i*2).to_f should return
+	  -HUGE_VAL (-Infinity).
+
 Mon Jun 15 18:48:41 2009  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (argf_each_line): should return self.  [ruby-core:23852]
diff --git a/bignum.c b/bignum.c
index 398d963aea..123eca7403 100644
--- a/bignum.c
+++ b/bignum.c
@@ -1233,7 +1233,10 @@ rb_big2dbl(VALUE x)
 
     if (isinf(d)) {
 	rb_warning("Bignum out of Float range");
-	d = HUGE_VAL;
+	if (signbit(d))
+	  d = -HUGE_VAL;
+	else
+	  d = HUGE_VAL;
     }
     return d;
 }