Matthijs de Ligt scored an own goal on his first start for new club Juventus in the International Champions Cup match against Inter Milan in Nanjing, China.
The mistake happened when the defender failed to deal with an inswinging corner from Inter's Stefano Sensi and stuck out a leg inside the six-yard box which made contact with the ball and beat his own goalkeeper.
It was a first start for De Ligt after he came on as a substitute in their 3-2 defeat against Tottenham at the weekend.
The Netherlands centre-back joined the Italian Serie A champions from Ajax for an initial fee of £67.8m.
The price made him the most expensive defender in Italian top-flight history.
The 19-year-old, who signed a five-year deal, had previously been linked with Manchester United and Barcelona.
The player also has a £134.8m release clause which will start from the third year of his contract.
De Ligt - Ajax's youngest ever captain - led the Eredivisie club to a domestic league and cup double last season.
He also took them to the Champions League semi-finals in which they lost to Tottenham in the final seconds in Amsterdam.
Cristiano Ronaldo equalised for Juventus with 22 minutes remaining in the pre-season friendly.