Brighton are believed to have paid in the region of £400,000 in compensation for England U18 international goalkeeper James Beadle.
The stopper, 17, joined the Seagulls in January after turning down a professional contract with Charlton.
Beadle is away with England at the moment for a four nations tournament in Zagreb.
Head coach Ryan Garry has named a 23-man party which also includes Crystal Palace keeper Joe Whitworth. Other Eagles players in the squad are Kaden Rodney and Jack Wells-Morrison.
They face Austria on June 7 and then Wales next Friday. The tournament concludes when England take on Croatia on June 13.