Sunderland have now kept nine clean sheets in 14 Championship games this season
Championship leaders Sunderland played out a second goalless draw in four days as they shared the points with Preston North End.
After the same result with 10 men at QPR on Saturday, the Black Cats were a little fortunate to claim a point in Lancashire.
Emil Riis came closest for the hosts with a curling shot, while Freddie Woodman denied Aaron Connolly in Sunderland's best moment.
But the draw and a seventh game unbeaten moved the visitors two points clear of Sheffield United at the top, with the gap to Leeds United in third up to four.
The point nudged North End up one place to 20th, although they are only out of the bottom three on goal difference.
North End belied their lowly position with the way they began the match on the front foot.
The hosts should have been ahead inside two minutes but neither Sam Greenwood or Kaine Kesler-Hayden could turn the ball in from inside the six-yard box.
Greenwood was then provider for another fine chance as his cross was met by a perfectly timed run from Mads Frokjaer-Jensen, but the Danish midfielder headed wide from 10 yards out.
In added time at the end of the half, Riis brought a terrific save from stand-in goalkeeper Simon Moore, who kept out his curling effort.
Sunderland struggled in the opening period to really impose themselves although they did have a couple of isolated moments as Wilson Isidor cut inside and hit the side-netting after Chris Rigg found him in space.
And Republic of Ireland striker Connolly was denied his first goal for the club by a fine save at close range by Woodman following good play from Trai Hume.
Black Cats bench can't find solution
Frokjaer-Jensen shot over from another promising position early in the second half as Preston continued to press.
Black Cats head coach Regis Le Bris was forced to turn to his bench just past the hour as he brought on regular wide men Romaine Mundle and Patrick Roberts, but the attacking threat did not really materialise as their play in the final third lacked quality despite being urged on by more than 5,000 fans from Wearside.
It was only in injury time that Woodman was tested as he pushed behind a shot from substitute Roberts.
However, the leaders' defensive resolve was again on display as they kept a ninth clean sheet in 14 Championship games.
Their recent run of games has involved four away games out of five and they have collected eight points from those travels with two wins and two draws.
It is now only one defeat in seven for Preston as they continue to improve under Paul Heckingbottom but they are still looking over their shoulders towards the bottom three.
'A good point' - Black Cats boss Le Bris
Preston North End manager Paul Heckingbottom told BBC Radio Lancashire:
"It's a point but it should have been three. I'm pleased with the level of the performance again. That has been our minimum as we have been performing really well.
"We had some really good chances first half and could have made the game really comfortable.
"While we are picking up points these last few games, we know we could have had a hell of a lot more."
Sunderland head coach Regis Le Bris told BBC Radio Newcastle:
"It was another tough away game against a strong team. We struggled during the first half to apply a high pressure and we conceded many situations.
"During the second half, it was much better. We changed the structure and the energy was better with the substitutions.
"It wasn't enough to score but at the end, it's a good point."
