diff --git a/lib/batch_api/error_wrapper.rb b/lib/batch_api/error_wrapper.rb
index 481d550..625daeb 100644
--- a/lib/batch_api/error_wrapper.rb
+++ b/lib/batch_api/error_wrapper.rb
@@ -27,7 +27,7 @@ def body
     #
     # Returns: an Array with the error body represented as JSON.
     def render
-      [status_code, RackMiddleware.content_type, [MultiJson.dump(body)]]
+      [status_code, RackMiddleware.content_type, [body.to_json]]
     end
 
     # Public: the status code to return for the given error.
diff --git a/lib/batch_api/rack_middleware.rb b/lib/batch_api/rack_middleware.rb
index 87a0177..f1e110e 100644
--- a/lib/batch_api/rack_middleware.rb
+++ b/lib/batch_api/rack_middleware.rb
@@ -10,7 +10,7 @@ def call(env)
         begin
           request = request_klass.new(env)
           result = BatchApi::Processor.new(request, @app).execute!
-          [200, self.class.content_type, [MultiJson.dump(result)]]
+          [200, self.class.content_type, [result.to_json]]
         rescue => err
           ErrorWrapper.new(err).render
         end