Kevin Magnussen was forced to hand his VF-19 over to Haas’ test driver after a headrest issue meant he was “struggling to see” while driving the car.
Magnussen was in action at the Circuit de Catalunya on Tuesday, Day Two of the opening pre-season test.
His running, though, was cut short when he was forced out of the car because of an issue with his headrest.
“I was sitting just with my head pointing forwards, so struggling to see,” Magnussen explained.
“The headrest was too far forward and when you sit like this and you brake, it’s not easy… to drive anymore.
“That’s something we need to fix.
“An easy fix but we don’t have the parts, we don’t have another headrest to fit, so we need to get that sorted.”
Haas test driver Pietro Fittipaldi was therefore handed a run late in the day.
He propped up the timesheets while Magnussen’s 1:19.206 meant he finished third fastest on the day.
The Dane added: “The early impression is that it is feeling good.
“There’s no big issues or inconsistencies and it’s nice to drive, predictable and those are positive things when you jump in a new car – that you don’t jump in and feel uncomfortable… you get in and you feel like at home.
“I’m sure it could be a lot worse than where we are.”