Pompey were denied a second successive home victory after conceding a late equaliser to Barnsley at Fratton Park.
It looked like they had done enough to secure all three points following Colby Bishop’s 16th goal of the season early in the second half.
But, with time running out, a long throw was hurled into the box and Bobby Thomas headed home the equaliser.
John Mousinho made three changes from the side that were narrowly beaten at Peterborough the previous week.
Di’Shon Bernard came straight into the starting line-up following his deadline loan switch from Manchester United, replacing the injured Zak Swanson at right-back.
Joe Morrell also returned from suspension and there was a place for Michael Jacobs, as Louis Thompson and Dane Scarlett dropped to the bench.
They were joined among the substitutes by Paddy Lane, who signed from Fleetwood earlier in the week.
It took a while for the game to really get going, with the opening stages often a chaotic affair and play becoming congested in the centre of the pitch.
Connor Ogilvie did well to throw himself in the path of a Jordan Williams shot, while Bishop could not quite flick Jacobs’ pass on target at the other end.
The hosts did have the ball in the back of the net midway through the half after Bishop had converted another Jacobs delivery.
Bit the flag had already been raised for a tight offside call and the celebrations of the Fratton faithful were cut short.
Barnsley had a chance of their own when an instinctive long-shot from Adam Phillips was tipped against the bar by the fingertips of Matt Macey.
And the keeper then came to the rescue again after Max Watters’ lay-off had sent Devante Cole racing through on goal.
It was Pompey who finished the half on top, however, and a neat Bishop pass released Owen Dale on the right.
He cut the ball back for Jacobs inside the area, only for Williams to throw himself in front of the shot to divert it behind.
Half Time: Pompey 0 Barnsley 0
The hosts came charging out of the blocks following the restart and Thomas did well to turn a Jacobs cross behind, with Bishop lurking at the back post.
And they did break the deadlock on 49 minutes, as Marlon Pack lifted the ball into the box and BISHOP slid in to send a left-footed volley into the bottom corner.
It might have got even better when Ryan Tunnicliffe cut back for Morrell, with Williams racing across to make a key block.
There was a great chance to double the lead when Brad Collins failed to collect Jacobs’ corner, but that seemed to take Bernard by surprise and he nodded wide from a few yards out.
Mousinho brought on Lane for his debut on 71 minutes, with Jacobs making way and both players receiving warm applause.
A monster Pack throw then caused problems in the opposition box and had to be nodded behind before Bernard was left with a simple finish.
Lane soon combined nicely with Bishop on the left side of the box and angled a low drive not too far past the post.
But the Blues received a huge let off when Morrell tripped Josh Martin on the edge of the box and referee Andy Woolmer immediately blew his whistle.
That was just before Cole slotted the ball into the net and Barnsley were furious, with their mood not helped by Herbie Kane blazing the free-kick high over the bar.
They did level late on 89 minutes, though, when a long throw from substitute Barry Cotter went all the way through to Thomas, who deftly flicked it home.
There were four minutes of added time for either side to find a winner, but there was to be no more late drama.
Pompey (4-3-3): Macey; Bernard, Raggett, Towler, Ogilvie; Tunnicliffe (Thompson 83), Pack (c), Morrell; Dale, Bishop, Jacobs (Lane 71)
Goals: Bishop 49
Subs not used: Oluwayemi, Hume, Hackett, Scarlett, Pigott
Barnsley (3-5-2): Collins; Thomas, Andersen (c), Kitching; Williams (Cotter 76), Phillips (Martin 64), Connell (Russell 76), Kane, Cadden; Watters (Shaw 64), Cole
Goals: Thomas 89
Booked: Kitching
Subs not used: Isted, Larkeche, Oduor
Referee: Andy Woolmer
Attendance: 17,854 (673 away fans)