Renault driver Kevin Magnussen says he misunderstood the regulations surrounding stopping at the weighbridge, believing the FIA was calling Red Bull's Daniil Kvyat.
Magnussen was requested to stop at the end of the second session but thought the command was solely for Kvyat, rather than both drivers.
As a result, Magnussen will have to start the Bahrain Grand Prix from the pit lane.
"I saw the red light to indicate the need to stop, which actually was for Daniil but in fact the same light was also for me, and that’s what I misunderstood," he said.
"I didn’t know that you could have two cars called in at the same time. When I saw Daniil pulling in at the red light, I slowed down in case they’d wave me through but they didn’t.
"In fact they wanted both of us. It’s done now, it happened, and let’s focus on getting ready for race day."