Celtic manager Ronny Deila wants his side to break the record for the fewest league goals conceded in a season for 96 years when they host Inverness Caledonian Thistle next weekend.
The Scottish Premiership champions were held to a 0-0 draw by St Johnstone, and another clean sheet against the Highlanders would mean they have conceded only 17 league goals all season.
Rangers conceded just 16 goals in the 1918/19 season, with the best since then 18 goals conceded by Aberdeen in 1970/71 and Celtic in 2001/02.
"I'm not so happy, but we didn't lose, we didn't concede any goals," Deila told BBC Scotland.
"We have an opportunity to break a clean sheet record - 17 goals is the lowest, I think - so it is going to be an important game when we host Inverness."
In Perth, Celtic were put under intense pressure for much of the match by the home side, with stand-in goalkeeper Lukasz Zaluska in inspired form.
James McFadden and Murray Davidson hit the post for Saints, who had defeated Celtic in Glasgow earlier in the season.
"I thought it was open, way too far open," said Deila. "I don't like when games are like that.
"That pitch is very poor, so hard to control the ball. We had some good performances, I think James Forrest was good on the right side.
"Lukasz (Zaluska) was unbelievable, very good for him and for us."
St Johnstone manager Tommy Wright was pleased to see his team move into fourth place, one point ahead of Dundee United.
Should Inverness CT win the Scottish Cup, the side finishing fourth would enter next season's Europa League qualifiers.
"To make 23 attempts against the best team in the country, tonight we showed a side of us that's often overlooked because we can play decent football, that was a 90-minute performance," said Wright.
"I don't think there was much bad finishing, it was good goalkeeping and bad luck.
"Yet we're pleased to win a point because Alan Mannus pulled off a great save at the end.
"Us older managers know how to get players through a season. I think we use the squad really well. That's why at this time of the season I think we are working really well.
"It puts us into fourth and it's up to Dundee United, they've got Inverness, a tough game tomorrow. It keeps us in the hunt.
"It's a point gained and a point Dundee United have to overcome."