Just 18 days after they were beaten 1-0 in the Champions League final against Bayern Munich in Lisbon, PSG were beaten as Lens celebrated a first victory in Ligue 1 for five years having returned to the top flight.
Pole Bulka, 20, tried to play the ball out along the floor to a team-mate, but Cameroonian forward Ignatius Gango got there first to fire into the top corner and give Lens a surprise lead in the 57th minute.
PSG were without several players due to positive tests for the virus including world-record signing Neymar and France striker Kylian Mbappe.
They could only field four players who started their 1-0 defeat by Bayern Munich in last month's Champions League final.