diff --git a/ChangeLog b/ChangeLog
index 6468c7c666..cf2c043114 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -15,6 +15,8 @@ Fri Aug 29 22:29:41 2008  Tadayoshi Funaba  <tadf@dotrb.org>
 
 	* numeric.c: added an alias (#magnitude).
 
+	* bignum.c: ditto.
+
 	* test/ruby/test_complex.rb: added assertions.
 
 	* test/ruby/test_rational.rb: ditto.
diff --git a/bignum.c b/bignum.c
index e9b7726dd3..14b9b1b762 100644
--- a/bignum.c
+++ b/bignum.c
@@ -2710,6 +2710,7 @@ Init_Bignum(void)
     rb_define_method(rb_cBignum, "hash", rb_big_hash, 0);
     rb_define_method(rb_cBignum, "to_f", rb_big_to_f, 0);
     rb_define_method(rb_cBignum, "abs", rb_big_abs, 0);
+    rb_define_method(rb_cBignum, "magnitude", rb_big_abs, 0);
     rb_define_method(rb_cBignum, "size", rb_big_size, 0);
     rb_define_method(rb_cBignum, "odd?", rb_big_odd_p, 0);
     rb_define_method(rb_cBignum, "even?", rb_big_even_p, 0);