Guingamp scored two of three second-half penalties to erase Neymar's opener and dump Paris Saint-Germain out of the Coupe de la Ligue.
Paris Saint-Germain's Coupe de la Ligue dominance came to a dramatic end as Marcus Thuram overcame one penalty miss to convert another at the death in Guingamp's eventful 2-1 away triumph.
Having squandered a chance to put the Ligue 1 strugglers ahead from the spot, Thuram later held his nerve to convert the winner from the spot in the 93rd minute.
PSG, the tournament's champions in each of the previous five campaigns, had earlier gone ahead in the 62nd minute, Neymar breaking the deadlock just over a minute after Thuram's initial miss.