diff --git a/actionpack/lib/action_view/helpers/number_helper.rb b/actionpack/lib/action_view/helpers/number_helper.rb
index 01fecc0f23..fccf004adf 100644
--- a/actionpack/lib/action_view/helpers/number_helper.rb
+++ b/actionpack/lib/action_view/helpers/number_helper.rb
@@ -13,6 +13,9 @@ module ActionView
     # unchanged if can't be converted into a valid number.
     module NumberHelper
 
+      DEFAULT_CURRENCY_VALUES = { :format => "%u%n", :unit => "$", :separator => ".", :delimiter => ",",
+                                  :precision => 2, :significant => false, :strip_insignificant_zeros => false }
+
       # Raised when argument +number+ param given to the helpers is invalid and
       # the option :raise is set to  +true+.
       class InvalidNumberError < StandardError
@@ -104,9 +107,9 @@ module ActionView
 
         defaults  = I18n.translate(:'number.format', :locale => options[:locale], :default => {})
         currency  = I18n.translate(:'number.currency.format', :locale => options[:locale], :default => {})
-        defaults  = defaults.merge(currency)
 
-        options = options.reverse_merge(defaults)
+        defaults  = DEFAULT_CURRENCY_VALUES.merge(defaults).merge!(currency)
+        options   = defaults.merge!(options)
 
         unit      = options.delete(:unit)
         format    = options.delete(:format)
diff --git a/actionpack/test/template/number_helper_i18n_test.rb b/actionpack/test/template/number_helper_i18n_test.rb
index f730a0d7f5..8561019461 100644
--- a/actionpack/test/template/number_helper_i18n_test.rb
+++ b/actionpack/test/template/number_helper_i18n_test.rb
@@ -45,6 +45,12 @@ class NumberHelperTest < ActionView::TestCase
     assert_equal("&$ - 10.00", number_to_currency(10, :locale => 'ts'))
   end
 
+  def test_number_to_currency_with_clean_i18n_settings
+    clean_i18n do
+      assert_equal("$10.00", number_to_currency(10))
+    end
+  end
+
   def test_number_with_precision
     #Delimiter was set to ""
     assert_equal("10000", number_with_precision(10000, :locale => 'ts'))
@@ -92,4 +98,15 @@ class NumberHelperTest < ActionView::TestCase
     #Significant was set to true with precision 2, with custom translated units
     assert_equal "4.3 cm", number_to_human(0.0432, :locale => 'ts', :units => :custom_units_for_number_to_human)
   end
+
+  private
+    def clean_i18n
+      load_path = I18n.load_path.dup
+      I18n.load_path.clear
+      I18n.reload!
+      yield
+    ensure
+      I18n.load_path = load_path
+      I18n.reload!
+    end
 end