diff --git a/test/serialization_test.rb b/test/serialization_test.rb
index f2c1faea..d778de7b 100644
--- a/test/serialization_test.rb
+++ b/test/serialization_test.rb
@@ -214,7 +214,8 @@ class RenderJsonTest < ActionController::TestCase
   def test_render_json_with_callback
     get :render_json_hello_world_with_callback
     assert_equal 'alert({"hello":"world"})', @response.body
-    assert_match %r(application/json|text/javascript), @response.content_type
+    # For JSONP, Rails 3 uses application/json, but Rails 4 uses text/javascript
+    assert_match %r(application/json|text/javascript), @response.content_type.to_s
   end
 
   def test_render_json_with_custom_content_type