Pompey avoided becoming an FA Cup scalp after battling from behind to win at National League North side Hereford.
They were poor before the break and Reeco Hackett’s error allowed Miles Storey to score against his former club.
But Hackett made amends by levelling the scores and it was a different story in the second half, with the Blues in total control.
Colby Bishop celebrated his 26th birthday by giving them the lead before Joe Pigott came off the bench to make sure the visitors would book their place in the second round.
Danny Cowley made two changes from the side that drew with Shrewsbury in the league last Saturday.
Hackett and Ronan Curtis were both recalled to the starting line-up, with Owen Dale and Dane Scarlett not being given permission to feature by their parent clubs.
Adam Payce, Koby Mottoh and Josh Dockerill were all named on the bench, just a day after helping the academy progress in the FA Youth Cup.
The visitors looked to get off to a bright start and when Clark Robertson’s corner was only partially cleared, Ryan Tunnicliffe’s shot was diverted into Dale Eve’s arms by Connor Ogilvie.
Then, after a spell of patient passing play from Pompey, a left-footed curler from Hackett had to be beaten away by the Bermuda international keeper.
It was Hereford who grabbed a shock lead midway though the first half, however, after being given a gift by their opponents.
Hackett was caught in possession by Storey, who raced away and slotted a confident finish past Josh Griffiths.
Not that the Blues were behind for too long, however, and HACKETT redeemed himself by levelling just nine minutes later.
Ogilvie’s cross from deep on the left was nodded down by Curtis for the forward – playing in a central role – who took a touch and lashed the ball home.
The clear-cut chances were not flowing, but there was one opportunity for Pompey to take the lead just before the break.
Josh Koroma swung in a corner from the right and it was met by Bishop, who could only send his header down into the turf and wide.
Half Time: Hereford 1 Pompey 1
There was a tactical tweak at the start of the second half, with Curtis moving central and Hackett heading out to the right.
The visitors were showing a lot more urgency and pinning their opponents back, but unable to find that bit of quality in the final third.
Pompey were totally dominant and were just finding it tough to break through with so many Hereford players behind the ball.
They almost found a way on the hour mark, with Curtis denied by a fine Orrin Pendley block as he tried to meet Zak Swanson’s cut-back.
Cowley responded with a double switch, as Curtis and Jay Mingi made way for Pigott and a fit-again Tom Lowery.
And they went ahead moments later, with a deft BISHOP header enough to divert Robertson’s corner into the net.
That was the cue for the Bulls to show a bit more attacking ambition, but it was still Pompey looking more likely to add to the scoring.
Another goal almost arrived when Griffiths’ long ball was flicked on by Pigott, only for Bishop to see his angled effort saved by Eve.
The victory was wrapped up moments later, however, as another Robertson corner was nodded on by Bishop and flicked into the net by PIGOTT.
Pompey kept attacking and Eve got down low to keep out a Koroma free-kick after the forward had been fouled.
That was it for the scoring, however, and the noisy travelling support could start looking ahead to who their side would get in Monday’s second round draw.
Hereford (4-4-2): Eve; Hodgkiss (c) (Derricott 90+2), Pendley, Amadi-Holloway, Evans; Mclean (Caton 86), Hanson, Thompson-Sommers (Thompson 65), Pinchard (Haines 65); Storey, Barnett
Goals: Storey 26
Booked: Evans
Subs not used: Wade, Osment, Summers, Klukowski, Campbell
Pompey (4-2-3-1): Griffiths; Swanson, Raggett, Robertson (c), Ogilvie (Hume 85); Mingi (Lowery 61), Tunnicliffe; Curtis (Pigott 61), Hackett, Koroma; Bishop
Goals: Hackett 33, Bishop 63, Pigott 80
Booked: Mingi, Koroma
Subs not used: Oluwayemi, Freeman, Morrison, Dockerill, Payce, Mottoh
Referee: Sebastian Stockbridge
Attendance: 4,912 (681 Pompey fans)