diff --git a/ChangeLog b/ChangeLog
index 568f6c2bf1..ed713eed6e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Thu Oct 10 11:11:33 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm.c (Init_VM): hide also the singleton class of frozen-core, not
+	  only frozen-core itself.
+
 Thu Oct 10 06:02:08 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* test/ruby/test_rand.rb: fix r43224. local variable `e' is
diff --git a/vm.c b/vm.c
index a43f3d6b20..0ade176c42 100644
--- a/vm.c
+++ b/vm.c
@@ -2285,6 +2285,9 @@ Init_VM(void)
     rb_define_method_id(klass, idProc, rb_block_proc, 0);
     rb_define_method_id(klass, idLambda, rb_block_lambda, 0);
     rb_obj_freeze(fcore);
+    RBASIC_CLEAR_CLASS(klass);
+    RCLASS_SET_SUPER(klass, 0);
+    rb_obj_freeze(klass);
     rb_gc_register_mark_object(fcore);
     rb_mRubyVMFrozenCore = fcore;