2 files changed, 18 insertions, 2 deletions
diff --git a/actionpack/lib/action_controller/metal/serialization.rb b/actionpack/lib/action_controller/metal/serialization.rb
index 9bb665a9ae..9fb49f512e 100644
--- a/actionpack/lib/action_controller/metal/serialization.rb
+++ b/actionpack/lib/action_controller/metal/serialization.rb
@@ -13,7 +13,9 @@ module ActionController
     end
 
     def _render_option_json(json, options)
-      json = json.active_model_serializer.new(json, serialization_scope) if json.respond_to?(:active_model_serializer)
+      if json.respond_to?(:active_model_serializer) && (serializer = json.active_model_serializer)
+        json = serializer.new(json, serialization_scope)
+      end
       super
     end
 
diff --git a/actionpack/test/controller/render_json_test.rb b/actionpack/test/controller/render_json_test.rb
index f886af1a95..dc09812ba3 100644
--- a/actionpack/test/controller/render_json_test.rb
+++ b/actionpack/test/controller/render_json_test.rb
@@ -26,8 +26,12 @@ class RenderJsonTest < ActionController::TestCase
   end
 
   class JsonSerializable
+    def initialize(skip=false)
+      @skip = skip
+    end
+
     def active_model_serializer
-      JsonSerializer
+      JsonSerializer unless @skip
     end
 
     def as_json(*)
@@ -89,6 +93,11 @@ class RenderJsonTest < ActionController::TestCase
       @current_user = Struct.new(:as_json).new(:current_user => true)
       render :json => JsonSerializable.new
     end
+
+    def render_json_with_serializer_api_but_without_serializer
+      @current_user = Struct.new(:as_json).new(:current_user => true)
+      render :json => JsonSerializable.new(true)
+    end
   end
 
   tests TestController
@@ -166,4 +175,9 @@ class RenderJsonTest < ActionController::TestCase
     assert_match '"scope":{"current_user":true}', @response.body
     assert_match '"object":{"serializable_object":true}', @response.body
   end
+
+  def test_render_json_with_serializer_api_but_without_serializer
+    get :render_json_with_serializer_api_but_without_serializer
+    assert_match '{"serializable_object":true}', @response.body
+  end
 end