Ferrari has been forced to build up a new chassis for Carlos Sainz after identifying a fuel system issue on the Spaniard's car after Friday's running in Barcelona.
Sainz had clocked in second in FP1 behind Scuderia teammate Charles Leclerc and P4 in FP2.
But a post-session investigation by Ferrari's crews revealed a fuel system issue that required a chassis change.
The Italian outfit reported the switch to FIA technical delegate Jo Bauer who allowed the team to break its curfew to undertake the F1-75 chassis change.
But Ferrari wasn't the only team whose crews worked overtime on Friday, with McLaren also building up a new chassis for Lando Norris.
The Briton had severely damaged the new updated floor on his MCL36 at the start of Friday's FP2, an incident that curtailed the McLaren driver's session.
While an initial analysis led McLaren to believe that only a repair of the new component would be necessary, a more in-depth investigation decided the team to change Norris' chassis.
The chassis changes do not warrant a sanction from the stewards for either Ferrari or McLaren.