clean sheet in a 1–0 home win against St Johnstone on 25 January 2017, a result which meant that Celtic equalled a 50-years-old club record 26 match unbeaten start to a domestic season (a record set by the Lisbon Lions in 1966–67). Gordon shut out his former club Hearts four days later, in a 4–0 home win, as Celtic broke the Lisbon Lions' unbeaten record. Premier League club Chelsea made an approach for Gordon during the January 2017 transfer window, which Celtic rejected. In March 2017, Gordon signed a contract with Celtic that ran until 2020. Gordon again shut out Hearts, in a 5–0 victory at Tynecastle on 2 April 2017, with the club clinching the Scottish Premiership title for the sixth successive season in record time with eight matches remaining. The team also broke a 100-years-old club record for an unbeaten start to a domestic season (36 matches in-a-row in 1916–17), with this win being their 37th domestic match unbeaten. Gordon was also in goal for Celtic in the 5–1 league win at Rangers on 29 April 2017, which was the club's biggest victory at Ibrox since 1897 (4–0 in 1897). On 21 May 2017, he kept a clean sheet in a 2–0 home win over Hearts in the final league match of the season, a result which meant Celtic completed a 38-match league season without losing a match, the first team to go an entire Scottish league season without a defeat since season 1898–99. He also won the Scottish Cup, after he played in the 2–1 final win against Aberdeen on 27 May 2017, which saw the club complete the domestic treble and finish a full 47-match domestic season without losing. Celtic topped the list for the most shut-outs in the SPFL with 19 clean sheets and held the joint best record with Hibernian for goals conceded in the SPFL with 25. Later years Celtic again won domestic trebles in 2017–18 and in 2018–19. This meant they had won all three competitions for three consecutive years, a feat known as the "treble treble". Gordon played regularly during that time but occasional high profile mistakes, such as in the UEFA Europa League against Fenerbahçe in 2015 and Red Bull Salzburg in 2018, posed doubts as to his reliability; he lost his place to Fraser Forster (returning from Southampton on loan) in 2019–20, and made only six first team appearances