diff --git a/ChangeLog b/ChangeLog
index a8a7cf1fc6..816eb80808 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sun Jul 15 21:07:43 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* bignum.c (get2comp): do nothing for empty Bignum.  [ruby-dev:31225]
+
 Sun Jul 15 19:05:28 2007  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* bignum.c (rb_cstr_to_inum): check leading non-digits.
diff --git a/bignum.c b/bignum.c
index 74659dd40d..36b4240def 100644
--- a/bignum.c
+++ b/bignum.c
@@ -97,7 +97,7 @@ bigtrunc(VALUE x)
     long len = RBIGNUM(x)->len;
     BDIGIT *ds = BDIGITS(x);
 
-    while (len-- && !ds[len]);
+    while (--len && !ds[len]);
     RBIGNUM(x)->len = ++len;
     return x;
 }
@@ -1038,6 +1038,7 @@ rb_big_neg(VALUE x)
     if (!RBIGNUM(x)->sign) get2comp(z);
     ds = BDIGITS(z);
     i = RBIGNUM(x)->len;
+    if (!i) return INT2FIX(~(SIGNED_VALUE)0);
     while (i--) {
 	ds[i] = ~ds[i];
     }