Liam Burt made an instant impact for Celtic as he returned to the club from Rangers by securing a penalty shoot-out win in the Scottish Challenge Cup.
The midfielder had signed a two-year contract hours before coming on as a substitute in Celtic Under-21s' 2-2 draw away to Queen's Park.
Burt had been part of Celtic's youth academy before joining Rangers.
But he made only three substitute appearances before being released by Celtic's city rivals this summer.
"He will be part of the Celtic reserve squad under the guidance of Tommy McIntyre and will be looking to push through towards the first team during the next two years," Celtic stated.
The Scotland Under-21 international had not featured for Rangers since December 2016 but made 19 appearances, four of them starts, on loan to Dumbarton as they were relegated from the Championship in 2018 and went on to play 10 times the following season for Alloa, who had beaten the Sons in the play-off to win promotion, starting three times.
Celtic's colts were two goals ahead within half an hour at the Pennycars Stadium in Airdrie through Jack Aitchison and Armstrong Okoflex, but the League Two side struck back through Salim Kouider-Aissa and Adam Martin, with Burt coming on immediately after the 72nd-minute equaliser.
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Heavy losses for Dons, Killie and Saints colts
The first round of the Challenge Cup was a mixed bag for Premiership colts teams, who won five and lost five against sides from the lower leagues.
Aberdeen Under-21s were thumped 6-0 away to Highland League side Brora Rangers, while their Kilmarnock counterparts were eased out 4-0 away to Lowland League team Kelty Hearts.
Cove Rangers, fresh from a 5-0 thrashing of Edinburgh City in their League Two debut after winning promotion, bounced back from going behind after two minutes to thump St Johnstone Under-21s 4-1 away from home, with captain Mitch Megginson scoring his fifth goal of the season.
Livingston's youngsters also suffered a bruising 3-1 loss to Highland League visitors Formartine United.
Meanwhile, despite Ryan Porteous giving his side an early lead as the centre-half returns from long-term injury and striker Oli Shaw chipping in with a late equaliser, Hibernian Under-21s slumped to a 4-3 defeat at home thanks to Matthew Cooper's stoppage-time winner for League Two side Elgin City.
Goals from Adedapo Awokoya-Mebude and Josh McPake were enough to secure a win for Rangers Under-21s, who fielded out-of-favour winger Eros Grezda, despite a late reply from 10-man Lowland League hosts Berwick Rangers.
Striker Aidan Keena scored twice for Hearts Under-21s as they overpowered League Two hosts Albion Rovers 4-1.
Midfielder Davis Keillor-Dunn scored one of the Ross County Under-21s goals as they beat Highland League hosts Fraserburgh 3-2 despite having Joel Macbeath dismissed for a second yellow card on the stroke of half-time.
Meanwhile, winger Cameron Breadner's first-half goal was enough to see St Mirren Under-21s through at the expense of Lowland League visitors East Kilbride.