partsMetadata[index] = fi
	}

	// Guess content-type from the extension if possible.
	if userDefined["content-type"] == "" {
		userDefined["content-type"] = mimedb.TypeByExtension(path.Ext(object))
	}

	// if storageClass is standard no need to save it as part of metadata.
	if userDefined[xhttp.AmzStorageClass] == storageclass.STANDARD {
		delete(userDefined, xhttp.AmzStorageClass)
	}