diff --git a/ChangeLog b/ChangeLog
index 2c54f2a0e5..c698c7da5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Jul 28 19:36:26 2009  Koichi Sasada  <ko1@atdot.net>
+
+	* proc.c (rb_method_entry_arity): support optimized method (send).
+
+	* test/ruby/test_method.rb: add a test for above.
+
 Tue Jul 28 04:34:05 2009  Hidetoshi NAGAI  <nagai@ai.kyutech.ac.jp>
 
 	* ext/tk/lib/extconf.rb: bug fix and ignore invalid Tcl/Tk libraries.
diff --git a/proc.c b/proc.c
index 9536ee63bf..3b83b17c3b 100644
--- a/proc.c
+++ b/proc.c
@@ -1487,6 +1487,14 @@ rb_method_entry_arity(const rb_method_entry_t *me)
 	      return -(iseq->argc + 1 + iseq->arg_post_len);
 	  }
       }
+      case VM_METHOD_TYPE_OPTIMIZED: {
+	  switch (me->body.optimize_type) {
+	    case OPTIMIZED_METHOD_TYPE_SEND:
+	      return -1;
+	    default:
+	      break;
+	  }
+      }
       default:
 	rb_bug("rb_method_entry_arity: invalid method entry type (%d)", me->type);
     }
diff --git a/test/ruby/test_method.rb b/test/ruby/test_method.rb
index dc44eee274..c60f7fa8a8 100644
--- a/test/ruby/test_method.rb
+++ b/test/ruby/test_method.rb
@@ -51,6 +51,10 @@ class TestMethod < Test::Unit::TestCase
     assert_equal(-3, method(:mo6).arity)
   end
 
+  def test_arity_special
+    assert_equal(-1, method(:__send__).arity)
+  end
+
   def test_unbind
     assert_equal(:derived, Derived.new.foo)
     um = Derived.new.method(:foo).unbind