The UK and EU will on Friday formally agree a post-Brexit deal to overhaul Northern Irish trade rules after lawmakers from both parties approved it despite a rebellion within Prime Minister Rishi Sunak's party.
UK foreign minister James Cleverly and EU Commission vice president Maros Sefcovic will sign off the "Windsor Framework" at a joint committee meeting in London.
The vote on the framework's so-called "Stormont brake" -- which hands Northern Irish lawmakers an effective veto over new European Union rules being implemented in the UK province -- won the backing of 515 MPs, with 29 opposed.
Despite Friday's show of unity, the new deal has reopened old divisions within Sunak's party.
Twenty-two Tory MPs -- including Johnson and fellow former leader Liz Truss -- opposed the brake in Wednesday's vote, while another 48 declined to vote.
MPs from Northern Ireland's largest pro-UK party, the Democratic Unionist Party (DUP), also voted against, suggesting that Sunak will struggle to get the party to resume power-sharing in Belfast.
The Stormont brake is a key cog in the new framework, which aims to reset strained ties between Britain and the bloc.
Northern Ireland is still in the European customs union and single market because of the need to keep an open border with EU member Ireland to the south as part of a 1998 peace deal.
Brexit figurehead Johnson called the framework "not acceptable" as he opposed it.