diff --git a/activesupport/lib/active_support/json/encoders/hash.rb b/activesupport/lib/active_support/json/encoders/hash.rb
index cfe21e4..db03437 100644
--- a/activesupport/lib/active_support/json/encoders/hash.rb
+++ b/activesupport/lib/active_support/json/encoders/hash.rb
@@ -31,6 +31,7 @@ class Hash
   # allowing the posts association in the User model to be converted to JSON
   # as well.
   def to_json(options = nil) #:nodoc:
+    options = options.to_h unless options.is_a? Hash
     hash = as_json(options)
 
     result = '{'
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index ab8e4e8..97ddb06 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -72,6 +72,10 @@ class TestJSONEncoding < Test::Unit::TestCase
     assert_equal %({\"a\":\"b\",\"c\":\"d\"}), sorted_json
   end
 
+  def test_hash_encoding_using_json
+    assert_equal %({\"a\":\"b\"}), JSON.dump(:a => :b)
+  end
+
   def test_utf8_string_encoded_properly_when_kcode_is_utf8
     with_kcode 'UTF8' do
       result = ActiveSupport::JSON.encode('€2.99')