Haas has made changes to its car for 2021 in reaction to Romain Grosjean's terrifying and fiery crash in Bahrain late last season.
The news comes ahead of the submission to the World Motor Sport Council on Friday of the stewards' report following an investigation into the incident.
"The report will come out tomorrow," Haas team boss Gunther Steiner said on Thursday.
"The biggest change we have done is to the (fuel) filler cap that is no longer fixed to the chassis, and we are also working on the headrest to make it smaller.
"The headrest is still there, but it can no longer get stuck when it comes off," he added.
"We decided to change them because we thought it was better to have something different," Steiner is quoted by the Italian publication Autosprint.
"You always learn from these situations. We followed everything about the rules, there was nothing wrong with the car, but what happened was a very strange accident where half of the chassis was torn away.
"If there is a better solution, we must always try to adopt it," he said.
