Workaround for file upload with validate quirk

Hi there just discovered a quirk when validating a form and uploading a file, if you select to upload a file, but the form still fails a validation, the form is returned however when posting again you have lost that uploaded file and there is no setting to tell the end user to reupload the file. How do we get around this, rather than letting them repost to only work out they need to reupload the file again ??