if a.Name == "" {
		return s
	}

	// If every character is printable ASCII, quoting is simple.
	allPrintable := true
	for _, r := range a.Name {
		// isWSP here should actually be isFWS,
		// but we don't support folding yet.
		if !isVchar(r) && !isWSP(r) || isMultibyte(r) {
			allPrintable = false
			break
		}
	}
	if allPrintable {
		return quoteString(a.Name) + " " + s
	}