Celtic fans were singing in the rain as Neil Lennon’s side came from a goal down to beat FK Sarajevo in Bosnia.
Goals from Mikey Johnston, Odsonne Edouard and Scott Sinclair should have the tie in the bag, but the win may have come at a cost as new boy Bolingoli hobbled off in the second half, closely followed by Johnston.
Lennon vowed to bring back the thunder in his first spell, and his second reign began with a thunderstorm in Bosnia.
Torrential rain battered down on the gallant band of faithful at the uncovered Asim Ferhatovic Hase Stadium, where Lennon raised a few eyebrows ahead of the game.
New Bhoy Christopher Jullien had to settle for a watching brief, as did comeback striker Leigh Griffiths, but left-back Boli Bolingoli-Mbombo started.
Anthony Ralston, the only right-back on the club’s books, was left on the bench.
Kristoffer Ajer moved out to right-back, while midfielder Nir Bitton filled in once again in central defence, as Celtic seemed to flit between a back four and a three.
The Hoops survived an early scare as the entire defence was caught out by a long ball over the top to Hebibovic who found himself with only the goalie to beat.
Thankfully, Bain stood up well to deny him but the opening goal was only delayed.
Just before the half-hour mark, a breakdown in communication saw Simunovic head needlessly by for a corner.
When the ball was swung in, Celtic were all at sea and Oremus pounced on a loose ball to slam home the opener.
Celtic, who had been lacking creativity and urgency, needed a quick response and Mikey Johnston provided it in the 35th minute.
Battling past two defenders, the young winger rattled in a shot from about 25 yards to level things, justifying Neil Lennon’s decision to give him the nod ahead of Scott Sinclair.
Celtic seemed to relax after that and it wasn’t long before Edouard linked with Forrest to carve out another chance, but the winger’s attempt with the outside of the boot flew over.
The start of the second half saw Edouard start the season where he left off, scoring a crucial goal on a sodden pitch to put Celtic 2-1 up.
An alert Brown nipped in to steal possession around 30 yards out. An incisive passing move saw Christie, back in action after his horrific facial injury, play in the Frenchman who calmly slotted home to put Celtic firmly in control of the tie.
Celtic continued to look edgy at the back where the defence’s tendency to play themselves into trouble had a few hearts in mouths.
Then, in the 85th minute, Lewis Morgan, who had come on for Johnston, hit the byline and fed Scott Sinclair, who brilliantly improvised to finish with a back heel.
A late run and shot from Edouard would have been the icing on the cake, but the goalie palmed away his effort.
Neil Lennon will be delighted to have started his second term at the helm with a convincing win.
Celtic: Bain, Simunovic, Bitton, Brown, Christie, Johnston, Edouard, Bolingoli, Ajer, McGregor, Forrest
Subs: Gordon, Jullien, Griffiths, Sinclair, Hayes, Morgan, Ralston.
FK Sarajevo: Kovacevic, Hodzic, Sabanovic, Lazic, Hebibovic, Ahmetovic, Rahmanovic, Velkoski, Milanovic, Serbecic, Oremus.
Subs: Dizdarevic, Sisic, Mustafic, Dokanovic, Guzina, Kurdic, Tatar.