Mercedes have been forced to change Valtteri Bottas' power unit after discovering an issue on his outlap during the first practice session for the Hungarian Grand Prix.
As Bottas toured the Hungaroring for the first time, Mercedes reported that misfires had occurred in his W10.
Bottas was immediately called back to the pits to have his engine changed, missing a chunk of time in FP1, although drizzle meant most teams were limited.
Mercedes confirmed that the new engine fitted has been used previously this season, meaning Bottas will not serve penalties as a result of the switch.
UPDATE: We will do a PU swap with Valtteri as a problem with the current unit has been identified. We are swapping in the other PU already in the pool. This will allow us more time to trace the problem outside the car. #HungarianGP#FP1pic.twitter.com/qdHXH1xARo