diff --git a/ChangeLog b/ChangeLog
index ef12ae4b04..93920e7c4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sat Aug 20 13:28:32 2011  Kazuki Tsujimoto  <kazuki@callcc.net>
+
+	* backport r33013 from trunk.
+
+	* iseq.c (iseq_s_disasm): fix a bug that may cause SEGV.
+
+	* test/ruby/test_method.rb (test_body): add a test for the above change.
+
 Sat Aug 20 10:43:24 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/stringio/stringio.c (strio_read): return new string if nil
diff --git a/iseq.c b/iseq.c
index c0cf98357f..9737d615c1 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1030,9 +1030,9 @@ iseq_s_disasm(VALUE klass, VALUE body)
 	rb_proc_t *proc;
 	VALUE iseqval;
 	GetProcPtr(body, proc);
-	iseqval = proc->block.iseq->self;
-	if (RUBY_VM_NORMAL_ISEQ_P(iseqval)) {
-	    ret = rb_iseq_disasm(iseqval);
+	iseq = proc->block.iseq;
+	if (RUBY_VM_NORMAL_ISEQ_P(iseq)) {
+	    ret = rb_iseq_disasm(iseq->self);
 	}
     }
     else if ((iseq = rb_method_get_iseq(body)) != 0) {
diff --git a/test/ruby/test_method.rb b/test/ruby/test_method.rb
index 1da32791f7..2cc0de5409 100644
--- a/test/ruby/test_method.rb
+++ b/test/ruby/test_method.rb
@@ -123,6 +123,7 @@ class TestMethod < Test::Unit::TestCase
     def o.foo; end
     assert_nothing_raised { RubyVM::InstructionSequence.disasm(o.method(:foo)) }
     assert_nothing_raised { RubyVM::InstructionSequence.disasm("x".method(:upcase)) }
+    assert_nothing_raised { RubyVM::InstructionSequence.disasm(method(:to_s).to_proc) }
   end
 
   def test_new