Celtic blundered their way out of the UEFA Cup as an error from Scotland goalkeeper Jonathan Gould set up Lyon for an assured march into the third round at Parkhead.
Gould's decision to race from his goal for a ball he never looked like reaching after 17 minutes presented Tony Vairelles with a vital away goal that put Lyon in control. Already trailing to Serge Blanc's strike in the opening leg, Celtic suddenly found themselves needing three goals.
Now John Barnes's men must lift themselves ahead of Sunday's Old Firm derby with Rangers at Ibrox.
Celtic restored fit-again Eyal Berkovic to the fold after a thigh problem, while Mark Burchill started with new signing Ian Wright ineligible.
Celtic had the ball in the net after 14 minutes after Lubomir Moravcik and Mark Viduka combined for Berkovic to slot in but the offside flag was raised.
CELTIC: Gould, Stubbs, Tebily, McNamara, Burley, Lambert, Riseth, Berkovic, Moravcik (Blinker 82), Viduka, Burchill. Subs Not Used: Kharine, Petta, Mjallby, Wieghorst, Petrov, Brattbakk. Booked: McNamara.
LYON: Coupet, Carteron, Laville, Bak, Violeau, Anderson (Uras 87), Dhorasoo (Malbranque 65), Vairelles, Blanc (Devaux 79), Delmotte, Linares. Subs Not Used: Govou, Caveglia, Ouerdi, Hugues. Booked: Violeau, Vairelles. Goals: Vairelles 17.
Referee: Georg Vardenne (Germany).
