Retrofit 2.0 Multipart Request, send boolean type in form data including file


I am trying to upload a file using retrofit 2.0. Apart from file, I have few other params to be send with form data which include a boolean type also. My request declaration is –

    Call<UploadResponse> uploadToServer(@Part("img_file";filename="image") RequestBody file,
                                             @Part("access_token") RequestBody sessionKey,
                                             @Part("is_final") Boolean isFinal,
                                             @Part("sequence_id") Integer sequenceId,
                                             @Part("entity_id") RequestBody entityId,
                                             @Part("image_type") RequestBody imageType);

I am using GsonConverterFactory. I tried 2 approaches –

(1) Instead of @Part("is_final") Boolean isFinal I used @Part("is_final") RequestBody isFinal and sending it with RequestBody.create(MediaType.parse("text/plain"), String.valueOf(true))

(2) Using @Part("is_final") Boolean isFinal and sending with Boolean.true.

In both the cases, “is_final” received on server side is Unicode or as a String instead of boolean value.

What is the best way to achieve this