SERVFAIL when two SOA in the domain

[Stephane Bortzmeyer]

One of my contacts noticed that you cannot query 42.fr's SOA with
BIND: SERVFAIL. Querying other types, or using Unbound (or Google
Public DNS) instead of BIND works.

The only thing special he sees is the double SOA:

% dig SOA 42.fr

; <<>> DiG 9.9.2-P1 <<>> SOA 42.fr
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 9894
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags: do; udp: 4096
;; QUESTION SECTION:
;42.fr.				IN	SOA

;; ANSWER SECTION:
42.fr.			2907	IN	SOA	ns1.42.fr. postmaster.42.fr. 2013032901 300 300 604800 86400
42.fr.			2907	IN	SOA	ns2.42.fr. postmaster.42.fr. 2013032901 300 300 604800 86400

;; AUTHORITY SECTION:
42.fr.			2897	IN	NS	ns1.42.fr.
42.fr.			2897	IN	NS	ns2.42.fr.

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)    <----- Unbound
;; WHEN: Thu Aug 29 20:21:51 2013
;; MSG SIZE  rcvd: 153

I'm not sure of what the RFC say about that...