Real Madrid had to settle for a 2-2 draw at home to Club Brugge, following a disastrous first half display against the Belgian side.
Zinedine Zidane's side went in 2-0 down at halt time, as defensive errors allowed Dennis Bonaventure two score twice before the break, with goals from Sergio Ramos and Casemiro securing a nervous point after the break.
Los Blancos lost 3-0 in their first Champions League game of the season, away at PSG, and they were behind after nine minutes as Percy Tau broke in behind a high offside line and squared for Emmanuel Bonaventure Dennis to tap home past Thibaut Courtois.
The hosts did not learn their lesson, as Bonaventure broke in behind himself five minutes before the break, an despite falling over at the key moment, he managed to poke home past Courtois.
The hosts were in determined mood after the break, with Luka Modric and Casemiro both bringing saves from former Liverpool goal keeper Simon Mignolet.
Ramos eventually got Zidane's side back in the game on 55 minutes, nodding home Karim Benzema's cross, and despite VAR proving inconclusive on an offside call against the Spanish international – the goal stood.
With time running out, Philippe Clement's side were unable to hold out, as Brazilian midfielder Casemiro powered home a header from Toni Kroos' whipped free kick.