diff --git a/ChangeLog b/ChangeLog
index e8da483215..6a07201574 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Sat Jun  9 17:21:48 2012  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* iseq.c (iseq_load): type is a symbol, and invalid as ID in common.
+
 Sat Jun  9 10:57:14 2012  Tanaka Akira  <akr@fsij.org>
 
 	* process.c (rb_exec_async_signal_safe): extracted from rb_exec_err.
diff --git a/iseq.c b/iseq.c
index f75911cab0..015e2a317f 100644
--- a/iseq.c
+++ b/iseq.c
@@ -516,11 +516,12 @@ iseq_load(VALUE self, VALUE data, VALUE parent, VALUE opt)
     }
 
     if (st_lookup(type_map, type, &iseq_type) == 0) {
-	const char *typename = rb_id2name(type);
+	ID typeid = SYM2ID(type);
+	const char *typename = rb_id2name(typeid);
 	if (typename)
 	    rb_raise(rb_eTypeError, "unsupport type: :%s", typename);
 	else
-	    rb_raise(rb_eTypeError, "unsupport type: %p", (void *)type);
+	    rb_raise(rb_eTypeError, "unsupport type: %p", (void *)typeid);
     }
 
     if (parent == Qnil) {
diff --git a/test/ruby/test_iseq.rb b/test/ruby/test_iseq.rb
index 2b25630e57..2fa8f2399a 100644
--- a/test/ruby/test_iseq.rb
+++ b/test/ruby/test_iseq.rb
@@ -8,4 +8,11 @@ class TestISeq < Test::Unit::TestCase
     bug5894 = '[ruby-dev:45130]'
     assert_normal_exit('p RubyVM::InstructionSequence.compile("1", "mac", "", 0).to_a', bug5894)
   end
+
+  def test_unsupport_type
+    ary = RubyVM::InstructionSequence.compile("p").to_a
+    ary[9] = :foobar
+    e = assert_raise(TypeError) {RubyVM::InstructionSequence.load(ary)}
+    assert_match(/:foobar/, e.message)
+  end if defined?(RubyVM::InstructionSequence.load)
 end