Celtic came from behind to beat HJK Helsinki 2-1 in the first leg of their Champions League qualifier at Parkhead, but the goal conceded leaves Neil Lennon's men with plenty to do next week in Finland.
The Hoops were made to pay for early profligacy less than two minutes into the second half when Rasmus Schuller fired the visitors ahead.
Parkhead striker Gary Hooper levelled in the 54th minute, before defender Charlie Mulgrew headed the winner seven minutes later.
HJK Helsinki looked out of their depth at the start when Celtic could, and should, have raced into a two-goal lead. Within 10 seconds Hooper came close with an angled shot after racing on to a Georgios Samaras head-flick, before Victor anyama failed to connect properly at the back post from a Kris Commons corner.
The Finnish side could hardly get out of their own half but in the 12th minute the home support held its breath when Wanyama barged into Juho Makela inside the Celtic box near the bye-line but Czech Republic referee Miroslav Zelinka awarded a goal-kick.
Wales international Joe Ledley then forced a good save from goalkeeper Ville Wallen with a low drive from the edge of the box but again the home side could not capitalise on the corner, giving the Finnish outfit the encouragement to force their way into the game.
The visitors' goal, two minutes after the restart, raised questions about the Hoops' defence. The lively right midfielder Sebastian Mannstrom played in Schuller and when his first effort from 10 yards was blocked by Fraser Forster, he took advantage of a fortuitous rebound to squeeze the ball in from a tight angle.
Commons then struck the post before the Scottish champions redressed the balance through Hooper after Samaras had picked up a Commons pass wide on the left and put a cross on a plate for the Englishman to tap into an empty net at the back post.
HJK Helsinki seemed to have lost their composure and just after the hour mark Mulgrew forced the Parkhead side into the lead when he met a Commons corner from the right and headed down and past Wallen from 10 yards.
With three minutes remaining, Hooper and James Forrest ran into each other inside the HJK Helsinki box after a Anthony Stokes pass had opened up the defence and left the two of them clear. It was an unusual moment of farce, but it was another missed opportunity missed which leaves Celtic's Champions League hopes on a knife-edge.