John Hartson revealed fellow Celtic forward Henrik Larsson opted out of taking a penalty, in the 2-0 win at Kilmarnock, through a lack of confidence.
The Swedish international had missed earlier chances and rejected the opportunity to open the scoring after Stilian Petrov was hauled down by Peter Canero.
Hartson stepped up instead and struck home before Paul Lambert added a second with a fine individual goal.
But the Welsh international admitted he was surprised at being given the chance from the spot by regular penalty-taker Larsson.