It doesn't work for you too:
dig @ns1.bugfix.potissima.com private._domainkey.bugfix.potissima.com TXT
; <<>> DiG 9.9.3-rpz2+rl.13208.13-P2-RedHat-9.9.3-4.P2.el6 <<>> @ns1.bugfix.potissima.com private._domainkey.bugfix.potissima.com TXT
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 33557
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1
;; WARNING: recursion requested but not available
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 2800
;; QUESTION SECTION:
;private._domainkey.bugfix.potissima.com. IN TXT
;; AUTHORITY SECTION:
bugfix.potissima.com. 1800 IN SOA ns1.bugfix.potissima.com. admin.bugfix.potissima.com. 2013091908 3600 1800 604800 1800
;; Query time: 44 msec
;; SERVER: 178.32.23.43#53(178.32.23.43)
;; WHEN: czw wrz 19 20:49:02 CEST 2013
;; MSG SIZE rcvd: 114