Toto Wolff says the changes Mercedes had to make to its new front wing before practice for Formula 1's Chinese Grand Prix did have an aerodynamic impact on its car.
Mercedes brought a modified front wing to Shanghai, featuring a different cut endplate to produce a curved trailing edge.
The aim of this was to help open up the space between the wing and the front tyre to help improve the outwash effect.
But following discussions with the FIA, and a physical inspection from head of single-seater technical matters Nikolas Tombazis, Mercedes was asked to make changes to the wing to ensure it complied with the rules.
The FIA believed the design - which left the trailing end of the front wing planes exposed - was in breach of rules that forbid elements from standing outside the endplate shadow.
Mercedes duly shaved back the wing edges and tipped them with round-edged plastic.
This was the only modification that the team had to do, as the endplate itself did not need any changes.
The rule that Mercedes fell foul of is aimed at ensuring sharp parts like wing elements are not in areas that could risk causing punctures in the event of contact of car damage.
Although Mercedes went on to secure a front row lock out with its modified wing, Wolff said that the changes were not without consequence.
Asked by Autosport about the impact of the tweak, Wolff said: "Well, it would be sad if you saw off a front wing and that hasn't got any impact.
"Then the aero doesn't work how it should.
"These things always have an impact."
Wolff said that Mercedes accepted the FIA's interpretation of the rules, following correspondence earlier this week in the form of a technical directive.
"If your interpretation of the rules is different to what the FIA's interpretation is, you need to accept the sporting authority," added Wolff.
"So it was a bit of a complication to modify hardware components on the field.
"But we have a really good group of people here who were able to do that under war conditions."