Wouldn't that salary have been arranged when he was signed as a relatively unknown 10 million signing from a French Ligue Un team? It was one of the most obscure French signings the manager has made and yet one of the best arguably.
It deserves upgrading of course but I think it's fair enough that it stays as it is until the time of renegotiating/extending. We don't cut their wages if they're not playing well so we shouldn't increase it until the aforementioned.