M'Bala Nzola's late penalty punished wasteful Inter and gave Serie A strugglers Spezia a shock 2-1 victory on Friday.
The Nerazzurri's slim title hopes are surely over after they were beaten by relegation-threatened Spezia for the first time at Stadio Alberto Picco.
Bartlomiej Dragowski saved an early Lautaro Martinez penalty, and that was a sign of things to come as toothless second-placed Inter dominated the majority of the game but lacked a cutting edge.
Daniel Maldini, on loan from Inter's fierce rivals Milan, put Spezia in front just under 10 minutes after coming on as a substitute at half-time, but Romelu Lukaku's late spot-kick looked to have salvaged a point.
Nzola had the final say by slotting home from 12 yards out after Denzel Dumfries barged Viktor Kovalenko over, ensuring Inter remain 15 points behind runaway leaders Napoli.