The left-back scored from inside the Reds' area with 18 minutes remaining after a dangerous Eric Dier cross from the right wasn't dealt with by the visitors' defence.
It cancelled out James Milner's penalty, which came just before half-time after Erik Lamela bundled over Roberto Firmino in the 18-yard box.
Liverpool certainly had the better of the first half and we were indebted to some fine goalkeeping from Michel Vorm to keep the score goalless in the opening half hour. He twice kept out Philippe Coutinho, including a brilliant fifth-minute reaction save, and was alert to deny Sadio Mane breaking through on a couple of occasions as well.