Jimmy Gopperth came off the bench to send Wasps top of the Premiership as his former club Newcastle Falcons were beaten 34-30 in an entertaining contest at Kingston Park.
Gopperth was a firm fans' favourite during three seasons with the Falcons before joining Leinster in 2013, but the fly-half returned to haunt the north-east club on Friday.
Wasps trailed 10-0 after only five minutes following a Sonatane Takulua try and a magnificent individual score from Marcus Watson, but Danny Cipriani ran on to his own clever kick to score and Christian Wade touched down soon after to give Dai Young's men a 12-10 advantage.
The Falcons led 22-21 at the end of an action-packed first half after Rob Vickers went over and Thomas Young marked his 50th appearance for Wasps with a five-pointer, which Cipriani converted.
Cipriani did not return for the second half after suffering what appeared to be an ankle injury, but his replacement Gopperth wasted no time in making an impact, diving over just five minutes after entering the fray.
Gopperth contributed five points from the tee and England centre Elliot Daly added a penalty from around 50 metres out, with Wasps hanging on while Guy Thompson was in the sin bin in a tense finale after Mark Wilson's try gave Newcastle hope.
Wasps move back above Saracens at the summit, leading the champions - who face Leicester Tigers in their game in hand on New Year's Day - by five points.