SpringBoot MultipartFile upload가 안되던 에러

Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed: 
org.springframework.web.multipart.MultipartException: Current request is not a multipart request] with root cause

 

$http({
    method: 'POST',
    url: Config.serverURL,
    data: formData,
    headers: {
        'Content-Type': undefined
    }
}).

ContentType을 명시하지말라는 말은 있었는데, 이게 진짜 undefined로 명시적으로 지워버려야 되는건진 몰랐다..