diff --git a/ChangeLog b/ChangeLog
index 96273c3fdc..2707f2826b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,4 +1,10 @@
-Tue Apr 30 12:30:18 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+Tue Apr 30 12:31:40 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* proc.c (mproc, mlambda): use frozen core methods instead of plain
+	  global methods, so that methods cannot be overridden.
+	  [ruby-core:54687] [Bug #8345]
+
+	* vm.c (Init_VM): define proc and lambda on the frozen core object.
 
 	* include/ruby/intern.h (rb_block_lambda): add declaration instead of
 	  deprecated rb_f_lambda.
diff --git a/proc.c b/proc.c
index 57d4ae05a9..6f0e83aada 100644
--- a/proc.c
+++ b/proc.c
@@ -2000,13 +2000,13 @@ method_inspect(VALUE method)
 static VALUE
 mproc(VALUE method)
 {
-    return rb_funcall(Qnil, rb_intern("proc"), 0);
+    return rb_funcall2(rb_mRubyVMFrozenCore, rb_intern("proc"), 0, 0);
 }
 
 static VALUE
 mlambda(VALUE method)
 {
-    return rb_funcall(Qnil, rb_intern("lambda"), 0);
+    return rb_funcall(rb_mRubyVMFrozenCore, rb_intern("lambda"), 0, 0);
 }
 
 static VALUE
diff --git a/test/ruby/test_proc.rb b/test/ruby/test_proc.rb
index dc426ddda5..a8933b0c76 100644
--- a/test/ruby/test_proc.rb
+++ b/test/ruby/test_proc.rb
@@ -1,4 +1,5 @@
 require 'test/unit'
+require_relative 'envutil'
 
 class TestProc < Test::Unit::TestCase
   def setup
@@ -1157,4 +1158,14 @@ class TestProc < Test::Unit::TestCase
       assert_equal('zot', o.method(:foo).to_proc.() {'zot'}, bug3792)
     }
   end
+
+  def test_overriden_lambda
+    bug8345 = '[ruby-core:54687] [Bug #8345]'
+    assert_normal_exit('def lambda; end; method(:puts).to_proc', bug8345)
+  end
+
+  def test_overriden_proc
+    bug8345 = '[ruby-core:54688] [Bug #8345]'
+    assert_normal_exit('def proc; end; ->{}.curry', bug8345)
+  end
 end
diff --git a/vm.c b/vm.c
index 5636f80752..ac86401c3d 100644
--- a/vm.c
+++ b/vm.c
@@ -2258,6 +2258,8 @@ Init_VM(void)
     rb_define_method_id(klass, id_core_hash_merge_ary, m_core_hash_merge_ary, 2);
     rb_define_method_id(klass, id_core_hash_merge_ptr, m_core_hash_merge_ptr, -1);
     rb_define_method_id(klass, id_core_hash_merge_kwd, m_core_hash_merge_kwd, 2);
+    rb_define_method(klass, "proc", rb_block_proc, 0);
+    rb_define_method(klass, "lambda", rb_block_lambda, 0);
     rb_obj_freeze(fcore);
     rb_gc_register_mark_object(fcore);
     rb_mRubyVMFrozenCore = fcore;