diff --git a/ChangeLog b/ChangeLog
index 41bd7422ad..0515989cac 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Tue Mar  5 10:19:09 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* numeric.c (rb_int_succ, rb_int_pred): shortcut optimization for
+	  Bignum.
+
 Tue Mar  5 10:02:48 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* lib/rubygems/ext/ext_conf_builder.rb (Gem::Ext::ExtConfBuilder.build):
diff --git a/numeric.c b/numeric.c
index fe85d6cc31..342527c01d 100644
--- a/numeric.c
+++ b/numeric.c
@@ -2390,6 +2390,9 @@ int_succ(VALUE num)
 	long i = FIX2LONG(num) + 1;
 	return LONG2NUM(i);
     }
+    if (RB_TYPE_P(num, T_BIGNUM)) {
+	return rb_big_plus(num, INT2FIX(1));
+    }
     return rb_funcall(num, '+', 1, INT2FIX(1));
 }
 
@@ -2410,6 +2413,9 @@ int_pred(VALUE num)
 	long i = FIX2LONG(num) - 1;
 	return LONG2NUM(i);
     }
+    if (RB_TYPE_P(num, T_BIGNUM)) {
+	return rb_big_minus(num, INT2FIX(1));
+    }
     return rb_funcall(num, '-', 1, INT2FIX(1));
 }