The 2009 250cc world champion is due to replace the injured Karel Abraham at the AB Motoracing team.
Abraham required surgery for a toe dislocation during practice in Catalunya with Michael van der Mark getting close to an agreement to ride Abraham's Open class Honda at the recent Dutch round.
Meanwhile Aoyama stood-in for Repsol Honda's Dani Pedrosa at three events earlier this season, claiming a best finish of eleventh.
The Japanese concluded his full time MotoGP career at the end of last season.