Portugal boss Fernando Santos has dismissed Guy Roux's suggestion that Renato Sanches is five or six years older than he claims.
Former Auxerre boss Roux had told Romanian broadcaster Dolce Sport that he believed new Bayern Munich midfielder Sanches, 18, had misrepresented his age.
"Yes, he says he is 18 years old but he must look at his past," he said. "His date of birth was declared a few years later. The date is not true. I believe he is 23 or 24 years old -- but he is a very good player."
The issue is reported to have arisen as a result of Sanches' parents separating and only registering the birth several years later.
Speaking at a news conference ahead of Portugal's Euro 2016 semifinal with Wales, Santos dismissed the questions over Sanches, who made his Benfica B debut in October 2014.
"Everyone knows Renato Sanches," Santos said. "He was born in Portugal like I was, and registered like I was. He is 18, I am 61. This is a joke."
Sanches, who agreed a move to Bayern from Benfica before Euro 2016, has made a positive impression this summer and says he is excited about the switch to the Allianz Arena.
"I am looking forward to Bayern, and Bayern can look forward to me," he told Sport Bild. "I have great ambitions -- I want to win titles with Bayern.
"I want to continue at Bayern where I left off at Benfica, I was a key player there. I want to help my team to have success as soon as possible. It makes me proud to play for Bayern in the future, a club with a great tradition in Europe."
He will play under Carlo Ancelotti at Bayern and said: "I will hopefully get even better under him."