diff --git a/activesupport/test/core_ext/object/duplicable_test.rb b/activesupport/test/core_ext/object/duplicable_test.rb
index 8ef2585fe9b9d370556c90126e7745949179f12a..154a10c1b35ed4aa5b249cdea1e41977d3c2e50f 100644
--- a/activesupport/test/core_ext/object/duplicable_test.rb
+++ b/activesupport/test/core_ext/object/duplicable_test.rb
@@ -5,8 +5,7 @@
 
 class DuplicableTest < ActiveSupport::TestCase
   RAISE_DUP = [method(:puts)]
-  ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new]
-  ALLOW_DUP << BigDecimal.new("4.56")
+  ALLOW_DUP = ["1", Object.new, /foo/, [], {}, Time.now, Class.new, Module.new, BigDecimal.new("4.56")]
 
   def test_duplicable
     rubinius_skip "* Method#dup is allowed at the moment on Rubinius\n" \