Sirius had taken the lead with 1–0 through Melker Heier when it seemed like the equalizer was coming.
After a corner kick, Neffati nodded the ball into the goal, at least according to the TV replays.
But just inside the goal line, Sirius captain Henrik Castegren kicked the ball out of the goal.
Referee Granit Maqedonci did not signal for a goal, despite the home team's protests.
It's in, no question about it, says Neffati, who celebrated the goal immediately.
When he sees the replay in the Max broadcast, he becomes even more convinced.
Instead, Leo Walta sealed the match with a dream goal in the 77th minute. The Sirius player volleyed directly from a corner kick and secured the three points.
Sirius has become something of a nightmare opponent for IFK Norrköping, who have not won a home match against the Uppsala team since 2018.
Norrköping is in 12th place with three points down to the relegation playoff spot and five points to the relegation line.
The next home match against IFK Göteborg, who are also on 27 points, will be a key match in the relegation battle.
Sirius climbed to eighth place with 37 points.