diff --git a/ast.c b/ast.c
index 585e495d39..ec9a98b3e1 100644
--- a/ast.c
+++ b/ast.c
@@ -614,8 +614,7 @@ Init_ast(void)
      */
     rb_cNode = rb_define_class_under(rb_mAST, "Node", rb_cObject);
 
-    rb_define_alloc_func(rb_cNode, rb_ast_node_alloc);
-    rb_undef_method(CLASS_OF(rb_cNode), "new");
+    rb_undef_alloc_func(rb_cNode);
     rb_define_singleton_method(rb_mAST, "parse", rb_ast_s_parse, 1);
     rb_define_singleton_method(rb_mAST, "parse_file", rb_ast_s_parse_file, 1);
     rb_define_method(rb_cNode, "type", rb_ast_node_type, 0);
diff --git a/test/ruby/test_ast.rb b/test/ruby/test_ast.rb
index f59b54c17a..27c6753a7e 100644
--- a/test/ruby/test_ast.rb
+++ b/test/ruby/test_ast.rb
@@ -129,6 +129,10 @@ class TestAst < Test::Unit::TestCase
     end
   end
 
+  def test_allocate
+    assert_raise(TypeError) {RubyVM::AST::Node.allocate}
+  end
+
   def test_column_with_long_heredoc_identifier
     term = "A"*257
     ast = RubyVM::AST.parse("<<-#{term}\n""ddddddd\n#{term}\n")