It was hardly the ideal preparation for Arsenal ahead of Sunday’s EFL Cup Final against Manchester City.
Arsene Wenger rested most of the players who will play at Wembley and it was a difficult night for the Gunners.
But they survived to make it through and focus now turns to the EFL Cup Final.
Arsenal was in control of this last-32 tie after they won in Sweden last week but they were stunned when Ostersund scored two goals in 69 seconds in the first half.
Ostersund cut the aggregate lead with goals from Hosam Aiesh and Ken Sema midway through the first half.
What should have been a comfortable night for the Gunners turned into a tricky one after 22 minutes when Aiesh gave Ostersunds FK a surprise lead.
Arsenal was booed off at half-time but they regained control of the tie a minute into the second half through Kolasinac.
The goal meant Ostersunds FK needed to score two goals and put Arsenal back in control, and despite a defeat on the night, they progressed by two goals on aggregate.