Fernando Alonso is concerned the banned high rear wing seen in Barcelona this weekend could have given Ferrari's rivals some clever ideas.
The FIA moved to ban Ferrari's interpretation of the rules when its new rear wing, debuted in Friday practice, was 3cm higher than normal due to a loophole about gurney flaps and slot-gap separators.
"The wing was one of the new parts we introduced here but the FIA decided that we couldn't use it," Spaniard Alonso is quoted by AS sports newspaper.
"It gave us a small improvement, maybe a tenth or a tenth and a half, so it is not something dramatic.
"There is nothing more to say; in F1 the rules are interpreted to the limit and sometimes you are allowed and sometimes you are not," he added.
Alonso insisted: "The important thing is that no one comes to Monaco with something similar and they are allowed to use it."