West Ham completed the club-record signing of Sebastien Haller earlier today.
The Hammers have paid £45m for his services.
According to reports from Bild and Kicker (translated by Sportwitness), the player has asked for a transfer clause in his contract that will allow him to leave for a Champions League club in future.
It was a condition from the player before he agreed to join the Hammers.
Haller is a quality striker who will improve West Ham a lot but the transfer clause in his contract leaves the Premier League club vulnerable to future offers from top clubs.