Lorient were amazed at Sunderland's £17m move for Didier Ndong, according to reports in France.
The Black Cats swooped for the midfielder on deadline day after being impressed by his displays in Ligue 1 last season.
Sunderland paid an initial £13.6m for Ndong, but French press claim that the fee for the transfer could reach £17m due to various performance-related bonuses.
And, according to L'Equipe, Lorient were staggered when Sunderland submitted such a big offer on the final day of the transfer window.
The 22-year-old was signed by the French club in January 2015 for under £1m after they plucked him from CS Sfaxien.