England centre Manu Tuilagi has been fined NZ$10,000 (£4,800) by Rugby World Cup officials for wearing a sponsored mouthguard.
Tuilagi, whose elder brother Alesana was sanctioned for the same offence last week, wore the Opro mouthguard in England's first two victories over Argentina and Georgia.
The International Rugby Board's policy is not to announce any fines that are imposed during the tournament but England were forced to admit the breach on Tuesday.
A Rugby Football Union spokesman said: "Manu wore a mouthguard where the branding was visible in the Georgia match when it shouldn't have been so therefore he's been fined NZ$10,000.
"It was a genuine error and he's trying now to focus on Saturday's game."
The fact both brothers were fined for the same offence has led to suggestions they deliberately flouted the IRB's strict advertising and sponsorship rules.
But Manu Tuilagi insisted they were not part of any ambush marketing campaign.
"I didn't know I had worn the wrong gumshield and I got fined for it," Tuilagi said.
"We always wore the same mouthguard, mine is the England one from the under-18s but it's got 'Opro' on the front and that's not allowed in the World Cup.
"I coloured it in with marker pen for the Romania game. I wore it against Argentina but they didn't know."