to_sentence should return a duplicate

2 files changed, 6 insertions, 1 deletions

diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index 7585137aca..baefa9cae4 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -26,7 +26,7 @@ class Array
       when 0
         ""
       when 1
-        self[0].to_s
+        self[0].to_s.dup
       when 2
         "#{self[0]}#{options[:two_words_connector]}#{self[1]}"
       else
diff --git a/activesupport/test/core_ext/array_ext_test.rb b/activesupport/test/core_ext/array_ext_test.rb
index d14ae39737..d7ab3ce605 100644
--- a/activesupport/test/core_ext/array_ext_test.rb
+++ b/activesupport/test/core_ext/array_ext_test.rb
@@ -82,6 +82,11 @@ class ArrayExtToSentenceTests < Test::Unit::TestCase
     assert_equal "one", ['one'].to_sentence
   end
 
+  def test_one_element_not_same_object
+    elements = ["one"]
+    assert_not_equal elements[0].object_id, elements.to_sentence.object_id
+  end
+
   def test_one_non_string_element
     assert_equal '1', [1].to_sentence
   end