Lewis Hamilton appears to be the first victim of the FIA's controversial helmet ban after being blocked from wearing a novelty lid in Malaysia.
In February the FIA announced drivers would be forced to stick to one helmet design to make it easier for fans to identify their heroes on track. The rule change received mostly negative feedback, with Sebastian Vettel, known for changing his designs with regularity while at Red Bull, branding it "a joke".
During Friday's first practice session in Sepang, Mercedes tweeted what appeared to be a novelty design for the reigning world champion, who was using the regular white and red design he adopted at the start of 2014.
Shortly after his FP1 ended with an engine issue, Hamilton tweeted his own image of the green and blue helmet - which appears to be the same design of his current helmet with a different colour scheme - but added he would be unable to wear it due to the new rules.