Multiple addresses via dhcpv6

[<aloysius eclipso eu>]

Hello,
I'm new to ipv6 and tried to have dnsmasq assign two addresses to my linux machine running networkmanager 
0.9.8.
NM apparently takes both addresses, adds it to the interface, then flushes it and adds the other one.

Since it's a bit weird I wondered if it's the expected behaviour or if could be a misconfiguration on my part.

Not sure if it's relevant, but one of the ranges is ULA.

Regard