Jan Vennegoor of Hesselink came off the bench to head a stoppage-time equaliser for Celtic in their Algarve Cup opener against Middlesbrough.
The Scottish Premier League champions were heading for defeat in Portugal when Darren O'Dea's underhit backpass gifted Jeremie Aliadiere a bizarre opener 19 minutes from time.
Substitute O'Dea's ill-advised pass to Mark Brown saw the goalkeeper's attempted clearance charged down by Aliadiere, the ball rebounding off the striker's feet and into the net.
Celtic had chances to score in the first half, Georgios Samaras twice heading too close to Ross Turnbull after fine wing play from Aiden McGeady.
Boro's best moment came from Josh Walker, whose left-foot strike forced a fine save from Brown, while Mohamed Shawky was twice off target from outside the area.
The second half - which featured a raft of substitions - was even more cagey, though Brown did well to get fingertips to an Aliadiere snapshot.
Turnbull was almost caught out by a curling Barry Robson free-kick but he recovered well to parry.
After both sides netted, there was still time for Paul McGowan to nearly strike a winner for Celtic.
BORO (First half): Turnbull; Young, Wheater, Pogatetz (capt), Grounds, Emnes, Walker, Shawky, Arca, Owens, Alves.
BORO (Second half): Turnbull; McMahon, Williams, Huth, Taylor; Walker (Tuncay 74), J Johnson, Digard, O'Neil (capt), A Johnson; Aliadiere.
Celtic: Brown M, Hinkel (Naylor 61), Wilson, Caldwell (Balde 61), McManus (O'Dea 61), Robson (Donati 66), Hartley, Brown S (Vennegoor of Hesselink 66), McGeady, McDonald (Caddis 66), Samaras.
Conditions Warm and humid
Website Boro Man of the Match First half Marvin Emnes, second half Gary O'Neil
Meanwhile in other news
A strong Boro side will take on Bank of Scotland Premier League champions Celtic, and although Mido will not be involved he has stressed that the reasons for his unavailability are out of his hands.
The player has released the following statement:
"I would like Boro supporters to know why I am not in the team for this evening's game in Portugal against Celtic.
"There have been ongoing problems regarding my visa which I hope to have sorted shortly. It could be that the Portuguese Embassy require up to a week to amend this situation, thus preventing my ability to travel to Portugal in the very immediate future." - Mido