The result left PSG, who are chasing a fifth successive league title, on seven points from four games after a 3-1 setback at Monaco in their last outing.
With striker Edinson Cavani left on the bench until the 68th minute after scoring twice in Uruguay's 4-0 World Cup qualifying win over Paraguay on Wednesday, PSG looked bereft of pace and ideas.
They took the lead in the 67th minute when Lucas Moura converted a penalty after Blaise Matuidi went down under an off-the-ball challenge.
Just when it seemed the home side would hang on for a laboured win, they were shocked as the adventurous visitors, who had missed two good chances in the first half, grabbed a deserved equaliser.
Kevin Malcuit delivered an inviting cross from the right and Slovenia striker Robert Beric chested it down before beating Kevin Trapp with a scrambled volley which bounced over the keeper.
(Writing by Zoran Milosavljevic; Editing by Toby Davis)
