Double Escaping in $ssl_client_s_dn

I have a client certificate which has non English characters in the subject, when I use the attribute $ssl_client_s_dn of ngx_http_ssl_module the value is escaped twice.

actual value = "L=D'UNCONG\x5CC3\x5C89"

expected value = "L="D'UNCONG\xC3\x89"

can someone kindly advise me on what I did wrong, How can I avoid this.