diff --git a/ChangeLog b/ChangeLog
index 714ceec3bf..1b18143237 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Feb 22 14:21:03 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* bignum.c (bignorm): x may not be a bignum.  [ruby-dev:28367]
+
 Wed Feb 22 09:22:40 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* eval.c (proc_alloc): add proper check for creation of a lambda
diff --git a/bignum.c b/bignum.c
index 587564929b..9cf7a3702f 100644
--- a/bignum.c
+++ b/bignum.c
@@ -92,7 +92,10 @@ rb_big_2comp(VALUE x)			/* get 2's complement */
 static VALUE
 bignorm(VALUE x)
 {
-    if (!FIXNUM_P(x)) {
+    if (FIXNUM_P(x)) {
+	return x;
+    }
+    else if (TYPE(x) == T_BIGNUM) {
 	long len = RBIGNUM(x)->len;
 	BDIGIT *ds = BDIGITS(x);