// not the MD5 of the part content does not change that.
	var completeETags []etag.ETag
	for _, part := range complMultipartUpload.Parts {
		ETag, err := etag.Parse(part.ETag)
		if err != nil {
			continue
		}
		completeETags = append(completeETags, ETag)
	}
	multipartETag := etag.Multipart(completeETags...)
	opts.UserDefined["etag"] = multipartETag.String()