The Melanesian Spearhead Group secretariat says MSG leaders felt it was a good idea for Fiji to be included in the signing of their agreement last Friday.
The signing for the first formal MSG constitution took place in Vanuatu.
Fiji's inclusion came despite earlier representations by MSG leaders that its military-government had been told it wouldn't be able to sign.
But the chairman of the secretariat, Johnny Koanapo, denies that Fiji's inclusion was only made possible by last-minute changes to the preamble of the agreement.
The wording of the preamble, relating to the signatories, changed from "government" to "state".
Mr Koanapo says the change meant that the agreement would accommodate everybody.
"Allowing members to sign, not as governments, but signing in as a state. I think it makes a bit of a difference as far as the legal experts are concerned. They analysed that and as far as that's concerned, they said it would be okay for everybody to sign."
Johnny Koanapo says MSG leaders had already decided to include Fiji before changes were made to the preamble