With the Reds leading the game 1-0, United were on the attack.
Romelu Lukaku launched in a tepid cross that should have been comfortably collected by the Brazilian.
However, he dropped the ball which bounced onto his knee which landed in front of Jesse Lingard.
The England international made no mistake from five yards out.
Anfield legend Robbie Fowler suggested before the game that Klopp’s acquisition of Alisson from Roma had made them serious title contenders.
He told The Mirror: “They needed a new keeper and a new centre half, and they went out and got them.
“Basically, they’ve addressed all their weaknesses, because in Fabinho they’ve also now got a defensive midfielder who can win headers in front of the defence, a big weakness before.
“Any team that is solid at the back and can score going forward have to be a threat.
“Liverpool have the best defensive record of team in the big five leagues in Europe, so it’s not controversial to say they are a massive threat to City.”