Had Roberto Firmino accidentally handled the ball in the build-up, Mohamed Salah's goal would have stood.
But what VAR Jonathan Moss suggested to referee Martin Atkinson was that the handball was deliberate.
He sees how Firmino moves his arm towards the ball while he is wrestling with Eric Dier and it keeps it under control, before Liverpool go on to score.
Atkinson checks his pitch-side monitor and concurs, chalking it off. It comes after a change from IFAB that a handball in the immediate build-up to a goal, accidental or not, would be disallowed.
However, a handball in the build-up to a goal would not be reviewed unless it was deliberate. This fell into the category of deliberate.
Overall VAR was used well in this game, from Son's Heung-min ruled-out opener to this disallowed goal for Firmino's handball.