diff --git a/actionview/lib/action_view/helpers/text_helper.rb b/actionview/lib/action_view/helpers/text_helper.rb
index 432693bc23b538284f25e23bb1942dc045ae2b82..58ce042f124db5879eab660b96d56f79dace85bd 100644
--- a/actionview/lib/action_view/helpers/text_helper.rb
+++ b/actionview/lib/action_view/helpers/text_helper.rb
@@ -204,12 +204,12 @@ def excerpt(text, phrase, options = {})
 
       # Attempts to pluralize the +singular+ word unless +count+ is 1. If
       # +plural+ is supplied, it will use that when count is > 1, otherwise
-      # it will use the Inflector to determine the plural form.
+      # it will use the Inflector to determine the plural form for the given locale,
+      # which defaults to I18n.locale
       #
-      # If passed an optional +locale:+ parameter, the word will be pluralized
-      # using rules defined for that language (you must define your own
-      # inflection rules for languages other than English).  See
-      # ActiveSupport::Inflector.pluralize
+      # The word will be pluralized using rules defined for the locale
+      # (you must define your own inflection rules for languages other than English).
+      # See ActiveSupport::Inflector.pluralize
       #
       #   pluralize(1, 'person')
       #   # => 1 person
@@ -217,7 +217,7 @@ def excerpt(text, phrase, options = {})
       #   pluralize(2, 'person')
       #   # => 2 people
       #
-      #   pluralize(3, 'person', 'users')
+      #   pluralize(3, 'person', plural: 'users')
       #   # => 3 users
       #
       #   pluralize(0, 'person')
@@ -225,7 +225,14 @@ def excerpt(text, phrase, options = {})
       #
       #   pluralize(2, 'Person', locale: :de)
       #   # => 2 Personen
-      def pluralize(count, singular, plural = nil, locale: nil)
+      def pluralize(count, singular, deprecated_plural = nil, plural: nil, locale: I18n.locale)
+        if deprecated_plural
+          ActiveSupport::Deprecation.warn("Passing plural as a positional argument " \
+            "is deprecated and will be removed in Rails 5.1. Use e.g. " \
+            "pluralize(1, 'person', plural: 'people') instead.")
+          plural ||= deprecated_plural
+        end
+
         word = if (count == 1 || count =~ /^1(\.0+)?$/)
           singular
         else
diff --git a/actionview/test/template/text_helper_test.rb b/actionview/test/template/text_helper_test.rb
index fae1965ffa31e460f888a981a1d5f720034f822d..fb98ac63302720511e332f4271b0cf26cc9d262b 100644
--- a/actionview/test/template/text_helper_test.rb
+++ b/actionview/test/template/text_helper_test.rb
@@ -379,24 +379,36 @@ def test_pluralization
     assert_equal("1.25 counts", pluralize('1.25', "count"))
     assert_equal("1.0 count", pluralize('1.0', "count"))
     assert_equal("1.00 count", pluralize('1.00', "count"))
-    assert_equal("2 counters", pluralize(2, "count", "counters"))
-    assert_equal("0 counters", pluralize(nil, "count", "counters"))
+    assert_equal("2 counters", pluralize(2, "count", plural: "counters"))
+    assert_equal("0 counters", pluralize(nil, "count", plural: "counters"))
     assert_equal("2 people", pluralize(2, "person"))
     assert_equal("10 buffaloes", pluralize(10, "buffalo"))
     assert_equal("1 berry", pluralize(1, "berry"))
     assert_equal("12 berries", pluralize(12, "berry"))
   end
 
-  def test_pluralization_with_locale
-    ActiveSupport::Inflector.inflections(:de) do |inflect|
-      inflect.plural(/(person)$/i, '\1en')
-      inflect.singular(/(person)en$/i, '\1')
-    end
+  def test_localized_pluralization
+    old_locale = I18n.locale
+
+    begin
+      I18n.locale = :de
+
+      ActiveSupport::Inflector.inflections(:de) do |inflect|
+        inflect.irregular 'region', 'regionen'
+      end
 
-    assert_equal("2 People", pluralize(2, "Person", locale: :en))
-    assert_equal("2 Personen", pluralize(2, "Person", locale: :de))
+      assert_equal("1 region",   pluralize(1, "region"))
+      assert_equal("2 regionen", pluralize(2, "region"))
+      assert_equal("2 regions",  pluralize(2, "region", locale: :en))
+    ensure
+      I18n.locale = old_locale
+    end
+  end
 
-    ActiveSupport::Inflector.inflections(:de).clear
+  def test_deprecated_plural_as_positional_argument
+    assert_deprecated do
+      pluralize(2, 'count', 'counters')
+    end
   end
 
   def test_cycle_class