Oscar Piastri won the Azerbaijan Grand Prix with a superb defensive drive ahead of Charles Leclerc.
However, it seems the squad began celebrating too early according to officials.
McLaren was found to have breached Article 34.13 of the sporting regulations, which covers safety in pit lane.
It makes specific mention that “Team personnel are only allowed in the pit lane immediately before they are required to work on a car and must withdraw as soon as the work is complete.”
Stewards found McLaren staff began moving towards parc ferme too early.
Having come under intense pressure from Leclerc for much of the race, in the closing laps Piastri edged clear, at which point it became clear he would win the race.
However, four drivers completed racing stops in the final three laps.
Max Verstappen, Daniel Ricciardo, and Esteban Ocon, stopped on Lap 49, and Pierre Gasly Lap 50 of the 51-lap race.
“While it is not unusual for team personnel to move towards the Parc Fermé area before the end of the race, McLaren had team members and equipment in the pit lane while other teams were still pitting and thus created a potentially unsafe condition.”
Having been found to have breached the regulations, McLaren was fined AUD $8260 (€5000).
Also in trouble were Verstappen, Ocon, Gasly, and Nico Hulkenberg, who were all warned for passing after the chequered flag.
While that in itself is not uncommon, the Azerbaijan Grand Prix finished under Virtual Safety Car conditions after Sergio Perez and Carlos Sainz crashed on the penultimate lap.
As such, overtaking at the time was prohibited, the four drivers escaping with a telling off.