[12] In 2016, he signed with Voždovac,[5] but closely moved on loan to Belgrade Zone League side Hajduk Beograd in last days of the summer transfer window.
[13] Ostojić joined Spartak Subotica at the beginning of 2017 and spent some period on trial, playing several friendly matches during the winter break off-season.
He signed a contract with club along with experienced Bojan Jović, who started the spring half-season as the first choice goalkeeper.
[14] Ostojić made his professional debut for new club under coach Andrey Chernyshov in the 24 fixture home match against Čukarički, played on 4 March 2017.
[21] Ostojić was called into the Serbia U20 under coach Milan Obradović in June 2017,[7] when he made his debut for the team in a friendly match against Israel.