diff --git a/activesupport/lib/active_support/core_ext/array/conversions.rb b/activesupport/lib/active_support/core_ext/array/conversions.rb
index e67b719ddb0fc8b8ddf1d8a2684f6afa2183c7a4..11c128da22f77406396d66cbcd5b576233f2cdfd 100644
--- a/activesupport/lib/active_support/core_ext/array/conversions.rb
+++ b/activesupport/lib/active_support/core_ext/array/conversions.rb
@@ -11,7 +11,8 @@ def to_sentence(options = {})
           options.assert_valid_keys(:connector, :skip_last_comma, :locale)
           
           default = I18n.translate(:'support.array.sentence_connector', :locale => options[:locale])
-          options.reverse_merge! :connector => default, :skip_last_comma => false
+          default_skip_last_comma = I18n.translate(:'support.array.skip_last_comma', :locale => options[:locale])
+          options.reverse_merge! :connector => default, :skip_last_comma => default_skip_last_comma
           options[:connector] = "#{options[:connector]} " unless options[:connector].nil? || options[:connector].strip == ''
 
           case length
diff --git a/activesupport/lib/active_support/locale/en-US.yml b/activesupport/lib/active_support/locale/en-US.yml
index 60ecb1d42a37d4b77e7f55441f0c927db6c66ba5..c31694b9d6dea1f45d2fa956b5b8abe99c46b0b0 100644
--- a/activesupport/lib/active_support/locale/en-US.yml
+++ b/activesupport/lib/active_support/locale/en-US.yml
@@ -29,3 +29,4 @@ en-US:
   support:
     array:
       sentence_connector: "and"
+      skip_last_comma: false
diff --git a/activesupport/lib/active_support/vendor/i18n-0.0.1/i18n/backend/simple.rb b/activesupport/lib/active_support/vendor/i18n-0.0.1/i18n/backend/simple.rb
index 2dbaf8a405c40d98d613d97e6e82c77089b47de4..30e3655b7bcf9492020b964deebb9f5e3936a07f 100644
--- a/activesupport/lib/active_support/vendor/i18n-0.0.1/i18n/backend/simple.rb
+++ b/activesupport/lib/active_support/vendor/i18n-0.0.1/i18n/backend/simple.rb
@@ -30,7 +30,13 @@ def translate(locale, key, options = {})
         options.delete(:default)
         values = options.reject{|name, value| reserved.include? name }
 
-        entry = lookup(locale, key, scope) || default(locale, default, options) || raise(I18n::MissingTranslationData.new(locale, key, options))
+        entry = lookup(locale, key, scope)
+        if entry.nil?
+          entry = default(locale, default, options)
+          if entry.nil?
+            raise(I18n::MissingTranslationData.new(locale, key, options))
+          end
+        end
         entry = pluralize locale, entry, count
         entry = interpolate locale, entry, values
         entry
@@ -83,7 +89,13 @@ def lookup(locale, key, scope = [])
           return unless key
           init_translations unless initialized?
           keys = I18n.send :normalize_translation_keys, locale, key, scope
-          keys.inject(translations){|result, k| result[k.to_sym] or return nil }
+          keys.inject(translations) do |result, k|
+            if (x = result[k.to_sym]).nil?
+              return nil
+            else
+              x
+            end
+          end
         end
       
         # Evaluates a default translation. 
diff --git a/activesupport/test/i18n_test.rb b/activesupport/test/i18n_test.rb
index 4b17e3c52368d2994f724faff38775f4ef74048b..db5bd5e088a38675153ce1b38adea9e38d6b7124 100644
--- a/activesupport/test/i18n_test.rb
+++ b/activesupport/test/i18n_test.rb
@@ -72,4 +72,20 @@ def test_time_am
   def test_time_pm
     assert_equal 'pm', I18n.translate(:'time.pm')
   end
+
+  def test_sentence_connector
+    assert_equal 'and', I18n.translate(:'support.array.sentence_connector')
+  end
+
+  def test_skip_last_comma
+    assert_equal false, I18n.translate(:'support.array.skip_last_comma')
+  end
+
+  def test_to_sentence
+    assert_equal 'a, b, and c', %w[a b c].to_sentence
+    I18n.backend.store_translations 'en-US', :support => { :array => { :skip_last_comma => true } }
+    assert_equal 'a, b and c', %w[a b c].to_sentence
+  ensure
+    I18n.backend.store_translations 'en-US', :support => { :array => { :skip_last_comma => false } }
+  end
 end