Chelsea have inserted a £35million release clause in the new contract signed by Ian Maatsen.
The left back signed a new contract when agreeing his loan to Borussia Dortmund for the season but his clause comes into play from June.
The defender made his debut for the Bundesliga side last weekend in a 3-0 victory against Darmstadt in which he started and played the entirety of the clash.
Maatsen, who joined Chelsea in 2018, made 15 appearances for Mauricio Pochettino's side this season but started just one Premier League fixture.