2 files changed, 24 insertions, 3 deletions
diff --git a/activesupport/lib/active_support/core_ext/object/duplicable.rb b/activesupport/lib/active_support/core_ext/object/duplicable.rb
index 9d044eba71..9d1630bb7c 100644
--- a/activesupport/lib/active_support/core_ext/object/duplicable.rb
+++ b/activesupport/lib/active_support/core_ext/object/duplicable.rb
@@ -104,3 +104,16 @@ class Module
     false
   end
 end
+
+require 'bigdecimal'
+class BigDecimal
+  begin
+    BigDecimal.new('4.56').dup
+
+    def duplicable?
+      true
+    end
+  rescue TypeError
+    # can't dup, so use superclass implementation
+  end
+end
diff --git a/activesupport/test/core_ext/duplicable_test.rb b/activesupport/test/core_ext/duplicable_test.rb
index e48e6a7c45..356b849adf 100644
--- a/activesupport/test/core_ext/duplicable_test.rb
+++ b/activesupport/test/core_ext/duplicable_test.rb
@@ -4,17 +4,25 @@ require 'active_support/core_ext/object/duplicable'
 require 'active_support/core_ext/numeric/time'
 
 class DuplicableTest < Test::Unit::TestCase
-  RAISE_DUP  = [nil, false, true, :symbol, 1, 2.3, BigDecimal.new('4.56'), 5.seconds]
+  RAISE_DUP  = [nil, false, true, :symbol, 1, 2.3, 5.seconds]
   YES = ['1', Object.new, /foo/, [], {}, Time.now]
   NO = [Class.new, Module.new]
 
+  begin
+    bd = BigDecimal.new('4.56')
+    YES << bd.dup
+  rescue TypeError
+    RAISE_DUP << bd
+  end
+
+
   def test_duplicable
     (RAISE_DUP + NO).each do |v|
       assert !v.duplicable?
     end
 
     YES.each do |v|
-      assert v.duplicable?
+      assert v.duplicable?, "#{v.class} should be duplicable"
     end
 
     (YES + NO).each do |v|
@@ -22,7 +30,7 @@ class DuplicableTest < Test::Unit::TestCase
     end
 
     RAISE_DUP.each do |v|
-      assert_raises(TypeError) do
+      assert_raises(TypeError, v.class.name) do
         v.dup
       end
     end