key := strings.ToLower(line[:idx])
		value := line[idx+1:]
		if _, ok := wantTrailers[key]; !ok {
			if cr.debug {
				fmt.Printf("Unknown key %q - expected on of %v\n", key, cr.trailers)
			}
			return errMalformedEncoding
		}
		cr.trailers.Set(key, value)
		delete(wantTrailers, key)
	}

	// Check if we got all we want.
	if len(wantTrailers) > 0 {
		return io.ErrUnexpectedEOF
	}
	return nil