Teplice 1-0 Celtic
Celtic progressed to the last 16 of the Uefa Cup despite one of their poorest European displays of recent times.
Jiri Masek blasted Teplice into a second-leg lead to give the Czechs hopes of causing a surprise.
But last season's beaten finalists, for whom Henrik Larsson sent two good chances straight at the keeper, held on anxiously for a 3-1 aggregate victory.
Celtic, already short of strikers through injury, suffered a further blow when Chris Sutton limped off.
Manager Martin O'Neill had made two changes by bringing in experienced duo Jackie McNamara and Paul Lambert for Stephen Pearson, who dropped to the bench, and the suspended Neil Lennon.
Striker Emil Rilke and midfielders Pavel Horvath and Pavel Kuchar were fit for Teplice, but forward Jiri Kowalik has been ruled out through injury.
Kick-off was delayed for 10 minutes by a power cut and Alan Thompson attempted to dim Teplice's lights further with two long-range efforts that were plucked out of the air by Tomas Postulka.
Henrik Larsson was next to test the Teplice goalkeeper, who again well held two long-range efforts from the Swede.
It was poor defending that allowed the Czechs to take a 35th-minute lead.
Stanislav Varga's defensive header felt straight into the path of Masek and the midfielder blasted the ball through Celtic goalkeeper Rab Douglas's arms from 18 yards.
Varga attempted to make amends shortly before the break, but the defender's header was straight at Postulka.
Lambert played a nice one-two inside the box with Thompson but fired straight at Postulka as Celtic tried to relieve the pressure after the break.
Teplice defender Karel Rada headed just over from five yards following a corner.
A fine cross from Didier Agathe found Larsson unmarked, but the striker's acrobatic volley from 16 yards was straight into the arms of the goalkeeper.
Celtic, who have lost John Hartson and Shaun Maloney to long-term injuries in recent days, suffered another blow when Sutton limped off after 70 minutes.
It was a rearguard effort by the Glasgow side as Teplice pushed forward in search of another surprise win, having disposed of Feyenoord and Kaiserslautern in previous rounds.
Larsson squandered a chance to settle Celtic's nerves, his low drive from 12 yards being saved by Postulka following a penalty-box scramble.
Teplice: Postulka, Leitner, Rada, Tesarik, Verbir, Dolezal, Skala, Hunal, Masek, Rilke, Kuchar.
Subs: Patrik Kolar, Jakub Kolar, Ryska, Styvar, Sigmund, Kostecka, Vorisek.
Celtic: Douglas, McNamara, Balde, Larsson, Thompson, Sutton, Lambert, Agathe, Petrov, Varga, Kennedy.
Subs: Marshall, Sylla, Valgaeren, Pearson, Wallace, Beattie, Smith.
Referee: Tom Ovrebo